Originally Posted by
Often1
The there is only one time & place to deal with this and it is with the FA and before the cabin door closes. Once the door is closed and the aircraft is full, there are no options.
This can all be handled discretly but fairly. Using words such as, I can't safely fit in what's left in the seat will force action.
Yup, this is pretty much when to handle the situation. Having a lot of experience in risk assessment, I probably could have predicted the outcome of the armrest lifting. Would have spoken up immediately. The seat he bought is about 17" wide, not the 20"+ the armrest lift provided. And OP bought a 17" wide seat, not 15", or whatever part of the love seat he ended up with.
A slick move might have been to raise the armrest between you and GF, and cozy-ing up to her.