Minecraft PE Multiplayer won't load?

Me and a friend want to play Minecraft PE together. She can be in my worlds, but I can't be in hers. Their worlds are also displayed to me, but it just doesn't load. I've tried several times and we have both multiplayer on.

Why can't I get in there or what can we do about it?

Try downloading the app again and logging in and something like that.

Unfortunately, if we delete the app, our worlds go away: / thanks anyway

I don't know exactly how. Handy makes a save state

Have to look on YouTube

Not really. You can save the worlds in a separate folder and that loading is either a bug or your internet upload is not good enough