I live in a small townhome development. And there are quite a few single women of various ages living here as well, plus a few couples & one or two single older men. I don't really know anyone here. I know who they are & where they live. But that's about it. I'm a pretty solitary old geezer myself. So I pretty-much avoid everyone.

As far as something to write on this lady's condolence page goes, I think you could paraphrase what you wrote here. You could say that, sadly, you didn't know her but that you happened to read her obituary. If you recall anything about her, such as having seen her periodically at the mailboxes or out for a walk, that sort of thing, you could mention that. You could also mention about the place where she worked as it related to your mom, if you feel comfortable doing so... any little tidbits you can come up with.

I sometimes reply to posts, here on PC, where no one else has replied & I don't really have anything specific to offer either. In those types of situations I often just write that I don't have anything specific to offer, but that I just wanted to let the poster know I read her / his post & I wish them well. Hopefully, as the old saying goes, it's the thought that counts...