BS”D
Regardless, we are not suckers and we don’t have to be taken advantage of regardless of someone’s real or imagined medical or psychological condition. If she took the seat for herself I’d also suspect illness. Holding it for her granddaughter is rishus and selfishness plain and simple.
I was pushed once in shul by a mentally ill man in Montreal and he later showed up in 770 and tried to do it again (not smart because he would have been handled by the community patrol had he so much as touched me). Why was he in shul in Montreal or able to get on a bus or train and get to 770? Because the misguided gabboim did not want to have him committed since it was hard to arrange kosher food for him in “Creedmoor d’Montreal”. Instead, others had to suffer from his violence.
Another misguided wannabe ohev Yisroel in Moscow managed to arrange for the release from psychiatric incarceration of an halachic shoiteh (we could not count him for minyan, plain and simple) who did not know where he was but did manage to burn down his apartment with his mother inside. Oh, how he loved seeing the Shabbos lights burning in shul – and we were very afraid he would burn the shul down too.