my friend just learned that her boyfriend basically cheated on her. so what can i do to help her?

Be there for her, do not give her advice. let her use you as her sound board and talk to you. just listen and be there ...you can't change what happened... you don't know how she feels and you don't know why he did it, so don't speculate....or call anyone down... be a good friend
listen....

Invite her over to stay at your house, rent some chick flicks, get some supplies for mani/pedicures, and get a lot of popcorn and candy. Then use it all. Lol

plan ways to get him back! ways to embrass him!
its fun but dnt actually do it Lol
just sumthing to laugh about.

Okay, what you do is this.
Have her sleep over
Have make-overs
Do nails
Get good movies
Pop some popcorn
Prank call the guy that cheated on her
Hope It Works Out! :P

sleep with her boyfriend

Spend time with her and convince her she is worth more than he can offer her. He is not a good person and she needs to move on.

just watch a movie together in ur jammies, and make some popcorn and buy some junk food, and have fun. :)

always be there when she needs someone. Treat her like a princess because normally people being cheated needs more attention and love as they think they've lost everything. Your friend might be emotional and complaining stuffs or maybe weeping every second. Be patient and loving. That's the point.

You can also invite her to do some shopping, eating out anything.