Years ago, I was fitted for a diaphragm ... and my experience was very similar to your girlfriend's, only I had a female LPN fitting me. It was amazing ... probably the longest time I've ever spent in a medical situation completely undressed.
I had gone for my annual breast and pelvic exam, and a friend had gotten a diaphragm and told me what a great little tool it was for when you had your period, or forgot to take your birth control pills ... so I decided to get one.
First, I forgot to tell the nurse until I was completely undressed and she had finished the breast exam. She sighed a bit and said we could fit it as part of the pelvic. As I scooted towards the end of the table, she took away my little paper sheet - it was the first time I've ever been completely uncovered for a breast/pelvic - and she told me I was going to have to watch to learn how to use it.
She proceeded with the pelvic (didn't warm the speculum at all, so I guess she wasn't fond of doing these fittings!) ... and she was extremely thorough with the bimanual exam and even did a rectal (my first - and I was only 19).
She had me sit up (still absolutely naked), and showed me a tray with diaphragms in several sizes - and told me that she'd have to fit me, then teach me how to use it. She had me lie back again with my feet in the stirrups and she inserted two fingers inside my vagina. She moved them around quite a bit -I suppose to assess the dimensions(?) deep inside me. Then she selected one of the diaphragms and spread me wide with two fingers, and pushed it in over my cervix. I could feel her run her finger around the edge to check for gaps ...
At this point, I was very aroused .. that had been a lot of looking and feeling around inside, and there wasn't much I could do to avoid it.
She had me stand and walk around a bit, to see if I could feel any movement inside .... I was so conscious of the movement of my breasts, the stickiness between my legs ... and then she had me lie back again, with my feet in the stirrups, while she inspected the fit again. Once again, two fingers deep inside, feeling all around ....
She pronounced the fit "good" but suggested I try the next size up ... just for comparison. She had me sit up, with my feet still in the stirrups, and she showed me how to hook my finger around the outside ring to pull the diaphragm out. Then, she reinserted it, folding it in half and pushing it back until it popped open and into place.
Then she said, "Okay, you try it." I was mortified - she said, "You have to learn, and for me to teach you, I have to watch. So, go on now ..."
I spread myself wide and inserted my finger, feeling around for the ring. She moved my knees further apart as I was doing this and stood, so she could get a clearer view. As I felt deeper inside, I began to panic that I would not be able to find it or get it out ... She must have realized this and told me to relax ... she put her hand over mine and inserted her finger over my two, and guided my finger to the ring.
At this point, I was uncomfortably stretched and humiliated at having her hand inside me as well as my own ... it was only two fingers, but two fingers from two different hands ....
She said that I should try to insert the larger one, because it would be easier to handle. She placed it at the entrance to my vagina and took my hand, helping me to grasp and push it in without fisting myself ... at this point, I was seriously doubting whether this was worth it!
Again, she had my lie back so she could check the fit, then stand and walk around. As soon as I stood, I knew this one was too big - it felt like it was holding me open ...
She had me get back on the table, this time face down, with my bottom up high and my chest on the table ... she again inserted two fingers inside my vagina and agreed that this one was too big ...
Going back to the first one, she had me sit up again ... at this point, I was accustomed to having nothing at all on (well, except my socks), and we had a conversation about spermicide, and she had me practice inserting and removing the diaphragm twice more.
The last time, she had me lie back again and spread me wide ... saying that she was afraid I had some allergy to the spermicide because my labia looked so red and swollen ... the truth was that I was just so very stimulated from having her touch me repeatedly that I could not help myself.
She gave me a prescription for some cream to quell the "irritation" I had, as well as an alternative spermicide, and told me to get dressed.
So yes - this was definitely one of the longer and more "interactive" exams I've ever had.