There was a half-hearted attempt to explain all the guests at her party by saying they were more interested in Callum's body than Bethany. Plus, bullies would normally wait until their victim was on her own rather than in a group of friends.
However, this lack of thought is another indication of Corrie's current lack of interest in building believable characters and storylines. I suppose we're to assume that Bethany's bullying problem was solved because the perpertrators were impressed that she apparently has an older boyfriend with a car... :searchme: