I think spitting on Sasha would be over the top and wouldn't make much sense. What Bayley did was perfect including calling her a stupid B.
I think because this angle burned for so long that when it happened the fans were cheering because it was happening. also because there was a problem with how they portrayed the relationship with Sasha back stabbing Bayley and demanding that Bayley raise her hand for example. Sasha was the bad friend and somewhat heeling.
Where what they did though worked was that Bayley beats the crap out of Sasha, then stops and leaves the ring as if he's spent. Then goes back and beats her up some more. The first part of the beating was frustration with her friend. The second part after the delay, that was hatred.