She needs to have a side job, or THIS as a side job, whatever the reasons they got divorce, her lawyer needs to make sure they cannot bring it during trial bc this is about custody nor the reasons they got divorce.  

You girlfriend needs to have a job that she can prove to the court she is in her feel, able to take care of the kids emotionally, economically etc. She must show that she has a good support system that would help her with anything related to the kid.  
Are you marrying her? that could help too. She can show that she has a stable home environment for the kiddo.  

What can the ex use against her? Websites? pictures? videos? I hope if she is working, she remove that stuff, she change her name and make a whole new persona.  

 
Depends of the state as well that you guys are located...

if she has the kids for 4 days a week, then that's really not a bad deal for each parent.
she needs to keep good detailed records of when she has them and keep all receipts on what she spends also.
she needs to have a job and proof of income.
she needs to stay out of trouble and stay clean.
any bad choices by her will be used against her by her ex.
put the kids first. always.
any time he asks her to take kids (on his days) do it and keep records.

it will take time, but keep doing the right thing and it will work out.  
if kids are safe with dad, then work your ass of while he has them.

10k is not a big deal for a lawyer.  but it is a lot of money to most people.

i think you can modify the parenting plan and child support without lawyers.
BUT you need to have good records of parenting time and have all your affairs in order.

it is a real pain in the ass to keep daily records. i did it for 5 years. just buy a daily planner and do it.

child support is a easy calculation based on parenting time and dad's income and mom's income. (keep records)

if she does not have a job and provable income then the judge will say "how can she raise kids with no income"?

my lawyer was NO HELP whatsoever.  at 275 an hour and over 10k when it was finally over.

kids need both parents as long as they are safe and "stable".....

i would recommend keeping the lawyer to get thru court (this time)..   keep good notes and ask a lot of questions.

then, next time it wont be as scary.

hope this helps a little.

good luck

IMO she needs to weigh the costs of continuing to fight for custody vs leaving things as is.  If the case was brought against her and she wants to maintain what she her current privileges then she has to fight tit for tat.  In other words she has to bring up his checkered past as well.  If the lawyer is worth it, then he should have a private investigator doing his due diligence on the father.  Tread carefully, worse case scenario is that both parents lose custody due to their past behaviors.

Is one parent established as the legal guardian, or is this an agreement they just made without paperwork? Unless it has been decided by the courts previously then neither parent has the legal right to claim that they are the custodial parent.  I do agree with one comment saying that she needs to have a legit side job if possible, otherwise the judge may just assume she is still providing.  In the majority of legal custody cases, most states will side with the mother.  

How old are the kids?  If they are 12 to 13 years of age then it could and may come down to the judge having them make the decision as to who they would prefer to live with.

I'd say if she's already 6 grand into it and can afford to, then fight for it.  The lawyer should be objective and tell her the truth on whether or not this is a winnable case, but I understand some are not.  Last, she can ask the lawyer to speak with the other lawyer and see if they can come to a mutual agreement/settlement.  It may work if the dad is tired of spending as well.  

Most attorneys that I know don't do divorce cases in part because they're so unpredictable and so nasty. If one party is determined to be an asshole, they can drag it out endlessly. The baby daddy seems to be intent on draining whatever resources she comes up with. Based on that, $4,000 seems like a wild guess.

Ask the attorney how they plan to handle baby daddy's tactics. How have they dealt with this before? If they just plan to react to this jerk, that seems like a good way to just throw money away.

The church business is a red flag, BTW. Anything more than a casual mention of the place would send me running. Attorney should know about her history, but if he's in a proselytizing church can be be non-judgemental?  Switching attorneys might cost you another grand, but could get you much more effective counsel and a better outcome.  

Good luck

Seriously, she is screwing around with a married man for starters - that being you.  Is that a healthy environment for kids?  Hey mom, who is that guy, just somebody I'm having an affair with, but we'll get married someday.  

You planning on getting a divorce?

Two or thee years is not behind her.  Was their drugs involved?  Is she paying support?  Even though you say he keeps changing the schedule, it shouldn't matter if she has a steady job and can get day care for those days that the schedule changes.

Just saying we're not hearing both sides of the story.  

...shared physical custody.  He may end up getting the kids 2-3 days a week anyway.  Most parents have joint legal custody - that means they both have a say as to the major decisions in the child's life.  Are you saying that his parents have SOLE legal custody and that she and the father are fighting for custody now that they no longer have drug problems?  You have to be more specific.

Briefly, my two cents:

1) In these types of cases, the lawyers of both parties have an interest in prolonging litigation.  
2) Judges always encourage mediation.  I would suggest that they request that the Judge entertain mediation --- if they haven't already done so already.  In fact, the Judge may order the case into mediation.
3) All litigation is time consuming and unpredictable.  A case like this could take several twists and turns.  Based on the above information, nobody could tell you what the odds of success are.  
4) She should start amassing letters of recommendation from as many people as possible.  Ideally, these recommendations are coming from people who are not relatives or friends --- coworkers, teachers, supervisors, and people who are respected in the community.  
5) Document all rehabilitation efforts to show that behavior has changed.  Express remorse.
6) If she doesn't have a good job, then she should attempt to find one.  If she doesn't have marketable skills, then she should attempt to obtain them.  Judges will consider ability to provide.
7) She might want to consider having a non profit or university take her case (as opposed to paying out of pocket).  Some non profits may take her case is she earns below their income thresholds.  All major universities have legal centers.  Many of them will allow their students to assist with cases (students gain needed real world experience).