I would pay her the cash.  Trying to pass fake 100's intentional or not, is huge.  Personally, I would feel bad and give her the money.  Just my two cents.  

You gave her counterfeit cash.  That's on you. And I get it was not intentional, but how can she know that.  

 
Now you can try to rationalize this from many angles:  
- It wasn't your fault - but it was  
- She should be more understanding - but she really doesn't have to be. What is a provider to do with bogus bills?  
- It's the principle of good customer service - but it's not.  
- Whatever POV you want to take - doesn't matter.  

 
If this was a dispute over thousands of dollars, you might want to fight this.  But come on.  Make it right with her and go back for lots of great orgasmic fun.   A few months down the road, after she's provided her services to you many, many times, you will both have a fond memory to laugh about.  

 
Life is good

 
The Cat

It’s a good thing you didn’t try to pass those bills at a proper establishment because you would probably be in jail now! I would chalk it up to my own stupidity and pay her whatever she requested. You caught a glimpse of her, so on a separate note you can  go back to see her for service if you think it’s worth it!

Some good comments here. I wrote it right after, and was a little worked up. Now it seems clearer! (in the ways you have eloquently written)

I posted a note, but I dont see it showing up. Thx for the responses. I was worked up right after, and everything you're saying makes sense to me now. I've contacted her and will get her the $.

So I guess I should ask how the hell you ended up with such fake bills?  Clearly she felt you were trying to scam her and for good reason.  Guys will pull that kind of crap.  I know a lady that was visiting Vegas and agreed to take casino chips as payment.  Bad move on her part, they were fake.  Always get your cash from the bank.  It's very rare for a fake bill to get past a bank, though it can happen.  

Look on the bright side, it could have been worse.  If you really feel bad, sending her the full amount is the right thing to do....with a nice note explaining what happened.  However, if you got those bills from other illegal activity, maybe don't go into much detail.  

Once I accidentally shorted a lady $40, so shit happens.  In that case, I immediately sent her the rest when she pointed it out.  Fortunately she knows me really well and realized it was probably an accident.   It's far worse to have a screwup the first time meeting someone.  Not exactly the best first impression.  

Please post a review so we can all avoid!

It’s your responsibility to do due diligence by inspecting your cash prior to your appointment. You still need to pay the poor woman. Being a musician does not excuse the fact you paid in fake bills. I check all my money. Ask her if she will accept venmo as a gift, or voluntary contribution, so you don’t have to see her, or drive back. You could also buy a prepaid Visa, or giftcard of her choice to send her the code for her to utilize. There’s, so many options this should never happen. $40 for a prostate care is an amazing value this lady is obviously working hard if she booked.