What should I tell her?

Why would somebody want to hurt their best friend? My friend, L like J and her bff S likes J but S said that she would never go for J because she knows how much L likes him, but than J and S have sex even though S said she wouldn't right to L's face and...

S knew how much L like dhim...How can I help make L feel better?

wow that was confusing... s sounds like a b*** and L needs to find a betetr bff. um as much as making her feel better I'd suggest just letting her have your shoulder to cry on for a while.. maybe a girls night out or something

When the s hits the fan, just be supportive to L.