A girl I've been talking to takes a long time to reply back to me. What does this mean?

So there's this girl that I like, and I think we have an interesting "relationship" I'm interested in her and I have a feeling she feels the same way. It's one of those things where we both can tell but we don't talk about it. A lot of times though, she takes up to hours to reply back to me on any social media. We mostly use snapchat though to talk. Does this mean she's ignoring me because she doesn't like me? Or is she just busy? I can't wrap my head around it because I always see her post stories after I send a snap to her and she still doesn't reply back.