That's a nice idea you got there
I really wonder if sorc already has the script in her mind, even if it's not yet depicted in a comic form.
Either way, I kinda imagine the story would be like this; Billy reports the fact that rainbow dash illegally takes the storm clouds, and when she is about to get expelled with firefly, Gilda comes in and admits that she did it instead, to save Dash. Billy probably feels bad about the fact that Gilda would get expelled and takes it back / saves it. Or the other probability is talking to Billy about Derpy being pregnant, and Billy starts taking second thoughts about it. Either way, I also believe that Gilda will breakup with Billy just like you said