My new advisor didn't reply to my email, is it a sign that she doesn't care?
Flippant version: It is normal AND it is a sign that the advisor doesn't care at all.

Less flippant version: I would wait a couple more days. Then, if still no response, I would ask around to see if the professor is sick/having a major life crisis/etc. If not, then I would conclude that they do not meet a reasonable standard of availability, and I would choose to work with someone else. There are few things more depressing in academia than colleagues who drop the ball and ignore you, especially when they are senior to you and you rely on them to make progress on your work. Life is too short to be working with someone who is not interested in working with you.