For example- Maybe she won't come to our party.
Remove the "maybe" and the example now reads
"She won't come to our party"
There is nothing hesitant or uncertain in that statement. Quite the opposite in fact, "she" either stoutly refuses to attend the party or the speaker is making a (pessimistic?) prediction.
- I won't do it!
(I refuse to do it)
- Maybe I won't do it
(I might not do it)
To express uncertainty in the future, you can use the modal verb might
“She might come to our party”
Like wouldn't for past situations, won't can be used to talk about refusal when it relates to present situations:
I can't get these pictures to download. I keep clicking on this icon, but they won't download.
It's no good trying to persuade him. He won't go and that's that.
Source: BBC Learning English
Wouldn't/would & won't/will for refusals and insistence