Be her support system
One of the simplest, yet more important things you can do for a friend going through a breakup is to be there for her. Listen to her, take her phone calls, watch cheesy chick flicks with her and bring her ice cream. Do anything that you think will make her feel better, especially in the first few post-breakup days.
Let her mope - but not too much
Depending on how serious the relationship was and how much she loved her ex, she will want to mope. Fair enough - she's in pain, but don't let her wallow for too long. She can still be sad and go work, get things done and be a productive member of society. Be sympathetic, but don't let her stay in sweatpants and avoid showers forever.
Don't trash her ex
Even if he deserves it, don't launch into a lengthy tirade about what a jerk he was right away, especially if she doesn't see it that way. If she's still stinging from being dumped, she may not feel like being lectured about her bad choice in men.
Get her out of the house
If you can, once she's had some time to mope (see above), try and get her out of the house. Go to the movies (no romantic comedies, please), plan a night out dancing or even go to a museum or art gallery - anything to take her mind off her ex.
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