Also in regards to Babs, this seems like a much bigger bully episode than Gilda was. While Gilda was a bully, the focus was more on the value of relationships between old friends and new friends, and expectations of them meeting. As Rainbow Dash pretty much said "If you can't treat my new friends nicely, it's over between us"
This one is really, truly about bullying and you could see what Babs was doing to harass the CMC in the song. Gilda was just mean spirited in general and, except for the antic with Granny Smith, you could say it was probably in her nature to steal the apple or yell at Fluttershy for bumping into her (yes, I had to bring that up, but it was a good example), or being a jerk to Pinkie, probably out of jealousy that Rainbow has other friends. Babs is deliberately being nasty...maybe out of pressure from the other two girls, but we'll have to see.