Pretty consistent with what you might see from someone with a depressive disorder - though there are many forms, and people exhibit symptoms differently. In the long term it would help to learn as much as you can about the topic.

The question isn't whether or not shes interested. The question is whether or not you can handle the emotional rollercoaster of being with someone that doesn't have their mental state under control. Thats up for you to decide.

When the opportunity to broach the subject presents itself, have a heart to heart conversation about the confusion and anxiety it causes you. The minimum she should provide is an idea of what to expect in the future, and how to best to approach the relationship when shes not feeling well. Asking how to support her is a good thing to do. You should also express your own needs and expectations.

If she isn't even able to have that conversation, then its time to move on. She isn't ready for a relationship and you aren't obligated to stick around while she works on herself.