If it were me, I would just let her know that you’re there for her whenever she needs you or wants to talk/vent but that you’re going to give her her space, too, in case she doesn’t feel like talking and then just leave it at that and check in maybe once a day or every couple days (whatever is regular for you guys) to see how she’s doing.

I know you want to take her pain away, but it’s actually really important that she feels it right now because that’s how she’ll eventually be able to let it go. Breakups suck, but they can be great catalysts for change in a positive way, so just let her feel her pain and sit with it for a bit and be there for her when she needs you, and that’ll help her more than even cheering her up will in the long term.