The 'maybe' rule
In social language, 'maybe' almost never means 'maybe'. It means: 'I don't want to, but I don't want to tell you no.' It's the most comfortable answer for the person saying it and the most confusing for the one receiving it. That's exactly why it exists.
The 3 versions
1) 'Maybe, let me check and get back to you' + confirms within 24h → real, there's interest. 2) 'Maybe' with nothing else → it's a soft no. 3) 'We'll see how I feel' or 'depends how the day goes' → she's not coming, but wants to keep you on hold in case nothing better comes up.
What to do
Don't push. Don't send 'so what's up?' the next day. Treat 'maybe' as a 'no' and move on with your plan. If she shows up, great. If not, you already had something else. Golden rule: never wait for someone who didn't commit.