Thanks so much for all the replies. There were so many that it was almost overwhelming to get through them all. I have sat down with my daughter to get some answers to many of your concerns.
First, YES, my daughter has seen a doctor. I seem to get this concern a lot. I have also updated (edited) my original post to include this.
Next, someone mentioned that the cup is supposed to spin/rotate. Hmn, didn't know that. So, I think that maybe a different cup may be in order here.
When I first discovered cups as an option, I did discuss it with my daughter. At first, she was apprehensive about using one, but said that she was willing to try.
She used the cup more than just once. She has tried it EVERY month - but only on the first day of her period. She will only use it for about 1/2 the day and then take it out. She will just use pads and tampons for the rest of that month.
I explained that the cervix can move up and down during the cycle and that she may have better success if she will at least attempt to use the cup during EVERY day of the entire period. I am thinking that by at least trying that, then she will be able to have a better understanding of her own body, which days the cup will work best for her, and will also be giving her more practice with using it.
I know that I have a harder time inserting my cup on the first day than I do on the second and third days. However, due to my cervix moving further down, by day 4 (and 5 if I last that long) my cervix makes it nearly impossible to get the cup in far enough to be comfortable. Usually, by then I switch to just a panty liner to collect the minimal amount that needs collecting.
As for taking advantage of this site, she has and does read, but if she does post, she will probably just post under my account. To my knowledge, she has never posted before.
She just finished her period for this month, and mainly only jmentioned the cup to me because we are not completely out of tampons and have only about 4-5 pads left (it took her 7 months to use ONE THOUSAND tampons and 250 pads). She is worried that there will not be any more, because when I got my husband to agree to let us spend the money on the cups, he only said yes because he thought we would no longer be spending money on tampons and pads.
After talking with my daughter today, she has agreed to try a different cup. I have told her that I will let her do her own research and figure out what cup she would like to have us purchase for her. I have showed her the comments to my original post to help her in the decision making process. If I had to choose for her, I think I would go with the Lady Cup. It seems smaller (which would help solve the issue of the bottom hanging out of her vaginal opening), and also more flexible (which should help with issue of it popping open before she gets it in far enough). I think she is leaning toward the Lady Cup, too. I guess we will see.
Oh, as for the stem - we cut it off. That was the FIRST thing she did after getting it. She got it and started within the week. As soon as she put it in for the first time, she took it immediately out, cleaned it, cut the stem off (pretty much all the way), and put it back in. She wore it all morning at school, took it out to empty at lunch, put it back in and wore it all afternoon until after school. She then took it out again to empty and wore it all evening until bed. Emptied and put back in for bed. That's when she woke up to find herself and her bed practically COVERED with blood. She was too upset to try again, she said her fear was that if she had that happen at school she would just have to die! Honestly, I can't say that I blame her for that.
She will only use it every month on the FIRST day of her period, and only until after school. Her heaviest day is the first day, after that she will bleed moderately heavy for about a week, and then the next week it will taper off each day until it ends. Even with using the cup for only 1/2 a day on the first day of her periods, she is having trouble getting the cup far enough in for it to feel comfortable. That's her other issue - wanting to not feel like the cup is hanging out of her vagina.
Anyway, thank you all, again, for your comments and concerns.