It sounds like she's living the good life!
In the case of house chickens, I totally get how having just one works. Extra cuddles and pampering!
I just thought it was uncommon to start with only one. Maybe that could be the case when rescuing one I suppose.
I think that you reach the limit of "too many" when caring for them is no longer joyful or pleasant. Most importantly, space limitations should be taken into account.
I started out with 4 pullets and slowly added more as I expanded my coop. Now I have 20 and that is my limit. Both because I do...