Thats a tough call travel.
LE is SO amazingly involved here in O-town that this type of info has unfortuantely become more than necc for screening. What else in an email could you address to her to validate indentity and an address? Have you seen a provider that knows your names and can recall your meeting to verify?
3 very consistant things I see on MANY providers personal websites now are:

* you must have seen a provider that can verify you (ie-RS2K ) only problem if the current provider can not contact her .. that option is now out
* you must provide some personal details so that info can be searched to prove you are who you say you are. Indetity is everything.
* no cell numbers- relates to all of above. They are anonymous can be picked up in any state by anyone LE or otherwise with all the prepaid programs

Recently there was a provider beaten mindless and injured brutally here in O-town. She screened and the gentleman checked out. Had she not been able to have info when she contacted the authorities that man would have been more than able to harm another lady. We take measures not only for safety but for legal issues.
Yes you want privacy and discretion. Everywhere you look someone is saying that a provider called his work home showed up asking begging or demanding $$$ or she was going to black mail him.
Last time I checked there are about 7 statutes in the state of Florida on harrassment regarding blackmail and the such.
Its a federal offense. I believe with the amazing ability on TER to find discreet well reviewed women this would narrow down the hacks and con artist who would seek to harm you .

Most of the contact sheets i've seen so far have a section for comments or a space where you may add any details about yourself that you feel like doing. If there's such a space like this on hers use it to explain the situation just as you did in your post and ask if there's any other type of in information she may possibly feel comfortable accepting in place of the phone number. At the least, explain why you are uncomfortable giving out the number(don't want calls showing up on the monthly bill because your SO sees the bill also)and possibly suggest(if you feel safe doing so) that you can provide the number for screening purposes as long as all communication is done via email. It can't hurt to ask, the most she can do is say no.

Above all, remember that if she declines to work around it or you don't feel right giving out a certain piece of information, move on. You both need to comfortable with the process. If one of you is not, then keep looking.

Snow

Get yourself a prepaid cell phone. No bills.

You might even be able to get it anonymously.