happened to me once on TWA...(i am very old!!)...i had the window seat, she had the aisle seat(two seat row)....had to put my arm above and around her shoulders to keep from getting my collar bones broken. i asked to be excused, asked the FA for another seat, and pointed to the impossible situation i was in. FA ageed, i sat in the back.
POS always have trouble.....its the b**th who started the shuffle who needed dressing down....anytime someone starts the "can you move so we can sit together" shuffle, inform the FA that if they wanted to sit together...they should have gotten their tickets sooner and at a higher price...like i must!!!