I know this probably sounds daft, so try not to flame me too hard!

I've booked a BA flight in F LHR-PHX-SAN for myself and a colleague. (This was on my BA PP Amex so happy with the avios!) The query is that the ticket has one booking ref with both of us named on it as it was one purchase but my colleague will be coming to airport later than I want to be there. I want to max my time enjoying the longe and experience. Can I check in separately to her and get my BP and go through to lounge, and then she checks in on her own when she gets there and we just meet up in lounge? Or are we required to check in together?

Thanks!