I think it dates back to their succesfull junior era, when Babos and her team said Timea is the more talaneted player between the two and Sloane took it hard.Wait, why/how are they frenemies? I need the tea
Sloane's draw looking straight out of 2013.
Back then they were talking some BS, like Timea having a top5 serve and her FH is fixed now, its like Nadal's FH
Probably there are no evidence for these, or one should dig really deep in the internet, but i remember vividly, cuz even back then i thought wtf.