How to work effectively with an unpredictable advisor?
She is a new professor, new to the job. Sometimes it may help to give her a indication what you would need from her, very diplomatic, very polite, but clear. If she does not follow up on that, consider switching supervisors. It is fine to back out from a supervisor that doesn't do their job well and do not promise to improve. It is your right to know what to expect from a supervision.