iirc they used to be really good friends and would go out drinking together so must have had a massive fall out. Diana didn’t get on with Ryan Murphy and Lea was Ryan’s absolute favourite so maybe that was why. Only Darren Criss and Jonathan Groff from the cast are still close with Lea.
Naya was arrested for domestic abuse. Blake Jenner abused Melissa Benoist..so messed up. Speaking of Melissa, apparently she hates Lea because she blames her for being dumped from Glee while Becca Tobin, one of Lea’s friends, was kept on. Apparently Lea didn’t like the Marley/Rachel comparisons. Marley was a boring character though, most of the season 4 newbies were.