I've never believed Serena and Meghan were best friends. Supposedly, they became friends in 2010 at that sporting event, but no photos were even posted of them together after that until late 2015 when Serena won Wimbledon and who was there to congratulate her, Meghan. Meghan was on the rich, white man hunt in the UK and was starting to set her sights on Harry.
After Wimbledon, we didn't hear about Serena and Meghan being besties until the wedding. I think Serena hung on to Meghan because she thought it would be cool to have a "Royal" friend, maybe get an invitation to a State Banquet, hang out in the Royal Box at Ascot. For Meghan it was having a big name friend. Serena hung on for quite a while, I think her mother and Venus finally made Serena see the light that she was being used. Meghan wasn't invited to the two baby showers Serena had nor did Meghan post anything publicly when Serena had her baby. If they were on good terms/friends we know Meghan would have made sure her message concerning Serena's baby would have been public.
I think Glo has gone AWOL after the car chase hoax.