Hmmm. This is a hard one. If only cats could talk. When she's inside does she ask to go out? Or is she only bothered when the doors open? She does sound like a lovely lady for sure.
Yes, it is very hard. She seems to stay in all day while we're at work, even though she can come and go through the cat flap, but she goes out when I open the door - and she does always poo in the garden, although she occasionally wees in the indoor litter tray. This may mean that she'd be unhappy having to use an indoor litter tray all the time or it may be a result of having lived rough for a few months.
As you say, if only they could talk. My ideal for Boo would be someone with a small safe outdoor area, I guess, but let's both have a ponder. I'll put her pic up tomorrow anyway.