slow motion on pc!

hello everybody! i wanna see if anyone has a fix for my problem. my girlfriend and i wanna play the game together but she has a problem. she plays in slow motion. everyone around her is normal speed but she's in slow motion. whenever she hops into a challenge it's normal speed again but once the challenge finishes then she plays in slow motion again. i've tried a lot of things but i'm pretty sure by now that it's not framerate/performance but a connection/server problem. can anyone help me?