I would have to say, from a guy's point of view, laying on my back with my girlfriend kneeling over my face is the most enjoyable. Well, most enjoyable for me. She says that she has problems not falling over, which I can understand, but if you hold onto her things should be good.

Try starting at her neck and give her a tongue bath down her spine and around the bottom. You may find some different spots to work on. I love it and my girlfirend has no problem with rimming. Gotta be clean!

Honestly - I think it all depends on a lot of things, yourselves, the place, mood, etc. Talk to her and experiment!!!!!

Personally, I like sitting on B/F lap (facing him, of course). This way we can look into eachother's eyes and at the same time I can control how much of him I want.

Have fun!

one position that isn't so rough on your neck is to have her lay down w/ her ass at the edge of the bed and you on your knees. this is also how i like to be in one of my fav sexual position.

also, sometimes my b/f will lay sideways to body. like ill lay down and say he's on my right. i keep my left leg down then he lays his head on my leg like a pillow and his face is facing my kitty
then i throw my other leg over his body.
this way is a lil easier like i said for your neck and also since your face is sideways its a lil easier to breathe.
hope this helps.