She's a lier and he's my friend?

my bestfriend has liked me since 5th grade and were just now finishing 7th. shortly after he he asked me out this year i said no but were still cool i told this other girl (girl B) that she sgould go out with him. she said no i dont like him like that and she looked grossed out. so he was in the hospitalfor around like 1 1/2 weeks and i found out today that they started going out while he was in the hospital. should i tell him shes a lier?