Quite agree with Bymonek's very accurate reply to this thread.
Monarch, First Choice, Excel, My Travel, Britannia its ALL the same wherever she ends up & B***DY hard work.
Try to imagine if you will the 'Trisha Show' mixed into 'Bar Med' on a rowdy Sat night....then put wings on it & NO means of escape!!
It quite literally just boils down to a different uniform or set of inflight safety & cabin service procedures. Ideally if she has had any experiences of flying as a passenger with either MON or FCA this could perhaps sway her final decision, or even which uniform she prefers!
I would say that Monarch has always been generally regarded within the industry as having a rather strict & regimented culture with many Temp junior horror stories to back it up.
First Choice however used to be similar in the old Air 2000 days with Glenda Lemont at the helm, but since all the funky & somewhat garish corporate identity changes, their's seems a much brighter (PINK!), fun & casual culture. I would say if she would like long haul then FCA has a great long haul product coming shortly with some nice routes.
Sounds like she has alot to offer by getting into two large reputable companies at the same time. Makes me think why not BA or Virgin?....much more civilised!
I wish her well.