Friend goes into quiet spells?

I've only been friends with this woman since the beginning of the year and we've hung out a slew of times and she's really cool.

I'm not sure what to think because she goes into these spells for weeks at a time where if I message her, she'll just reply with a few words...Then a week later, she'll text me all day non stop as if we're best of friends.

I've told her face to face I know she gets busy at work etc., but does she need time alone and doesn't want to be close friends. I have so much to chat with her about and she oftentimes dismisses my messages -- then she'll message me out of the blue all day long and be sure involved.

I don't mind not talking to her all the time, but she seems just distant and rejects my convo a lot.

IS this maybe a sign of depression?? SHe's become close to me so she can be honest if something is wrong, or she's being private, but should I bother giving this friendship the benefit of the doubt or hold back in thinking she's a good friend?

I can write her a whole message sometimes and she just replies "ok, good" and then I don't hear from her for weeks.