The thin outer ring of a female condom should remain outside of the vagina.

My 2 cents.

I remember when the female condom first came out. Hey, it was an option. There  was a curvy little thing named Pixie Deville that I would see every so often in the Wilshire area, many years ago, at pay by the hour hot tub place. I believe it was actually a place used a lot by some sleazy dating show. Anyway she used a female condom and she used it totally wrong. She pushed the whole thing up in there. So basically BBFS with the condom like a diaphragm. Didn’t matter either way because she did Greek without as well. Pixie wasn’t the best looking gal, but she did pretty much everything, at a low rate and at a sleazy place that set the mood. Wish she hadn’t moved away. She was a sure thing. Anybody else remember Ms Pixie Deville?
As for the female condom, even if used as intended it just seemed like banging a ziplock bag in a pussy.

There are a few profiles that will indicate she is ok using them.  But I've found providers who will be open to the idea if you approach the topic gently.   Some tips (no pun intended):  

 
1. Buy your own. If she's never used them before, she probably won't have any.  
2. Do not ask her about this during screening!  
3. Be prepared for her to reject the request.
4. I always bring recent test results with me as well. It adds credibility to my request.  
5. How to use:
A. Most experienced users advise to toss the little ring that goes at the bottom and not use it. It makes inserting and positioning the FC difficult and awkward and in my experience it's useless anyway.  
B. Suggest she put the FC over a small dildo or toy to make insertion easy.  
C. Leave about 1/4" to 1/2" inch of material outside the labia. You want that "skirt" to ensure your entry goes inside.  
D. She may have to hold it open when you penetrate.  
E. As with all condoms, replace after you finish. And use a separate FC for vaginal vs anal.  

 
Finally, if you write a review, be sure to tag the Female Condom box and mention it in your write up.  

 
Life is good

 
The Cat