M.B.
L.,
Give her a cup with maybe 2MM (very little) water on the bottom. Help her then let her practice on her own. It's a great non-staining way for her to learn to do this.
Above all, don't worry. She's going to 'get it' in her own time. Like a lot of kids, she'll transition.
If you are truly worried about the bottles and dental issues (after age 3 I believe for pacifier, but don't know about age for bottles since the nipples collapse), then gradually give her cups and let her know her supply of bottles is 'dwindling' until you have only one that you use regularly, and it actually wears out and can't be used anymore. She'll understand and know she has to make the transition. What doesn't exist can't be used.
Good luck,
M.