1, maybe she also wants you to use it. If she knows you are using it, she must know that you like her, but it doesn't mean she likes you, too. It needs your further expression.

2, or he doesn't mind you using it, because even if she doesn't like it, it's a happy thing that someone likes her.

3, or she is calm and doesn't care at all. Anyone who uses her has an attitude and is casual.