If you want to continue to be friends with her, the best thing you can do is respect her boundaries. If she asks you not to call her at work, then don't call her while she is working. That is a pretty standard boundary. I also ask that no one call me at work. I'm working, which means I'm busy and not available. If she says she needs space, that means that, in general, you probably need to call/text her less often because she doesn't have as much time for you as you may like. That doesn't mean she doesn't want to be your friend; it means she has other things and people in her life that she needs to give time and attention to. Are you in therapy? Learning boundaries is a really common thing that people work on in therapy.