Minecraft screen stuck at Loading Terrain

On my friend's minecraft, whenever she tries to go onto a server, the game "stutters" and leaves her on "Loading Terrain" for a long time. She has tried re installing minecraft, restarting computer, and tons of other things.

Hm

Did she try to delete the .minecraft folder?

Located here ==> C:\Users\[the user]\AppData\Roaming\.minecraft

This also deletes the singleplayer saves and the server list so back those up if needed.