iMessage doesn't sync anymore between MacBook and iPhone

[johannnn]

Since a few weeks ago my GFs iMessage is behaving weird. My phone now has two conversations with her in Messages.app, one that only sends to her MacBook, and the other that only sends to her iPhone.
I have two questions
1) How is this fixed? They are still logged in to the same iCloud account, I don't get why they are now separated
2) I now have two conversations with text and media on my iPhone, is it possible to merge these two?

Thanks!

 

[AustinIllini]

I'm not sure how to merge them. With these situations it's always best to just plan going forward. First, I would make sure iMessage is in the Accounts for Messages on the mac (In Messages, go to Preferences and check the accounts). After that, i would go into your iPhone and under messages check to make sure her mac is under "Text Forwarding".