My sister had been feeling down after a breakup.
I'm really sorry to hear that. What's worse is the best thing for breakups, the only thing that really helps, is time passing by. But the people who are hurting, in the moment, they can't really understand or accept that. So, you feel like you have to help and do something, when in reality it's probably best you don't smother them and that they have space. I hope she feels better, though.
I talked her into coming over to my apartment to watch funny movies and eat junk food to get her mind off of it.
Yeah, that's a good idea. That's always a solid way to go about it. My roommate had a breakup 6 months ago. I tried not to give any advice that was too specific, because the best solution always has to come from that person themselves. My roommate ended up just focusing on himself as much as possible, diving into artistic endeavors, trying to work out, etc.