Tell her that it really bothers (or hurts, or irks or disturbs or irritates) you that she doesn’t take anything that you say seriously, whether it be your opinion, your ideas, your desires or whatever else it may be. Then give her a few concrete examples of when she had done that (because she is likely to deny that she has ever done that). Then ask her if she really values your friendship and what she is prepared to do to fix this situation.
At that point, she may tell you to buzz off or go to he*l. In that case, you need to drop her as a friend, because she isn’t one. If, on the other hand she starts crying and tells you that she didn’t realize that she was doing this, reassure her that you were not intending to hurt her feelings or to criticize her, just tell her that you’ve been hurt by some of her comments and lack of support and then ask her what she thinks you guys should do to rectify this situation.
Sounds like she’s probably a drama queen who needs to have lots and lots of attention and she probably doesn’t care (or know how) to have a real, give and take symbiotic realtionship with another person. In that case, she really isn’t your friend and you’d be better off without her.