Breaking up is always hard and even more difficult when one of the partners involved (in this case her, is sending you mixed messages)
The only way to find out what her real intent is to ask her flat out. Speculating will not help and as you've mentioned you do not believe her to be totally honest with you.
In regard to what you would do- ask yourself this questions -
if you are back with her in a romantic relationship will you trust her completely or will you always have wonder what is she up to.
if you remain just friends- what is it that that relationship will bring in your life that you are lacking if she is not your "friend" Another question to ask yourself is - would there be a temptation at some point to rekindle the romantic relationship once again?