Why didn't she return my messages?

There are several reasons: 1. She is busy with other things and will send you a message when she is free.

If this is the reason, you have to wait patiently.

It's not impossible that there is something wrong with the mobile phone. In that case, I think you'd better call her directly.

Maybe she really doesn't want to contact you. Then, you can keep in touch with her, deepen each other's impression, or give in.

Bless you.