Give her space.
Let her talk about her feelings.
Cook her food.
Cuddle with her until she falls asleep.
Remind her how much you care.
Bring her coffee (or a bottle of wine).
Let her cry on your shoulder.
Give her a massage.
Make her orgasm.
Give her a pep talk about how wonderful she is.
Surprise her with flowers.
Let her rant for as long as she needs (and rant along with her).