It is pretty much common knowledge that Charlie doesn't fancy either of them and won't be interested in seeing either of them after the show, so why doesn't she just tell them outright and end this nonsense?
It's all on her IMO.
What, she has to become responsible for sorting their stupid little feud?
Im sure they wouldn't like eachother regardless but she could make things easier for them in there by telling them both she's not interested, she is stringing them along for her own ends.
I think she's made it pretty clear to both of them that she doesn't fancy them, but likes them and wants to be friends