It might not be personal, might just be that, her 'plate is full'. Maybe something came up in her life.
I don't know about continuing the fourth step with someone new as I'm not in AA nor have I ever had a sponsor or worked the steps. Maybe when you find a new sponsor, you can start over with step one, two, and three, and just kind of breeze thru them since you've already done them. Kind of a refresher course for the first three steps before you start the fourth step with a new sponsor. By then you'd have gotten to know her and she wouldn't be so new, maybe you'd feel comfortable enough to do your fourth step.
I hope you have good fortune finding another sponsor.
