Aye, sounds like she doesn't get what a RA is. Perhaps no one has told her what an RA is expected to do, and how they are expected to work. I'd first try tactfully presenting this information to her clearly and directly.
If I were in your shoes, I would have probably tried to subtly let her know as you have already, but eventually if that did not work I would make it more obvious as to my displeasure; whether or not I'd do it tactfully would be dependent on whether or not she's genuinely clueless or just lazy.
For example, if I had a student that came to me asking me what to do and it was something that would be clear to her if she had read the literature, I'd say "You need to read ABC before you come to me. If you have any questions with ABC pertaining to XYZ (where XYZ is the subject ABC covers pertaining to the work/ problem she is asking about>, let me know." If she did so through an email, I might be nice this first time and give her some general direction on where in the literature to pay attention. I'd then see how she responds... if she doesn't show that she made the effort to figure out from the literature what she's suppose to do or how to solve the particular problem, then I'd rinse and repeat then next time she seeks a hand-holding session.
Hopefully she'd get the clue after the second time around, but if she doesn't then I'd probably seek the consul of someone with more authority and experience in such matters, in this case my adviser. Your adviser is there for you to learn from, and I'm sure he/she has had plenty of experience having to deal with similar scenarios with his/her own graduate student RAs. If you approach your adviser about the issue from an "asking advice" point of view, letting him/her know what you've tried to do so far to solve the problem and making it clear that you'd like to try to learn to resolve the matter on your own without his/her direct involvement/ "lighting of fire", then that reflects well on you. Plus it would give your adviser the opportunity to shed his/her own wisdom on how to handle such situations and give you strategies and solutions you can try.
If everything you try short of seeking help from your adviser fails, I suspect it's more that she does not have the right personality to be a good RA, and to overcome such an obstacle is not going to be easy because it would require fundamentally changing the way she learns and thinks, things that have been ingrained in her ways. Some people just aren't cut out for research oriented, open-ended, independent work environments- where it's not about just searching for the answers to questions, but discovering what the questions are that you must search for answers to.
I would at least make it clear to her that if she plans to pursue graduate studies, she needs to learn to adapt to a different paradigm of learning than she's used to. You could directly tell her what is expected of graduate level RAs. I learned a great deal about what I can expect from graduate school through my undergraduate research experiences, all by simply hearing directly from the current graduate students during the summer REU program orientation about what is expected of them from their advisers.
When I did my undergraduate research, I was like the first RA you mentioned, I was self-motivated and require minimal hand holding. But I had been a self taught programmer years before I started college, and by the time I started my undergrad research, I was already well adept in the skills of speed self-learning; learning what I have to learn in order to accomplish or perform some task or goal, given a relatively short amount of time, and minimal direction/ hand holding/ supervision.
