"Bo Place Like Home" took place in the third season and after Bo made her peace with her now dementia addled human mother the woman that raised Bo was never mentioned again.

I've decided that since in my re-factored version of the episode, "Can't Bo Home Again", Bo and Mary come to an understanding and Mary is fully aware of Bo being fae, there is no reason why Mary can't make another appearance later in the show. In fact, wouldn't a mother want to check on her child? Even one that's been on her own for ten years? Actually, especially because Bo has been on her own for 10 years!

I believe that this Mary would spend some time after this episode coming to terms with what she had gone through and then made a few decisions. The main one being that she no longer has a reason to stay in town. So like Bo, she's on a quest to live the life she chooses but one of her first stops is Fae-town to visit her little girl. At some point in the fourth season Mary Dennis would make an appearance and discover that Bo lives in a house that should be condemned and apparently was abducted by her real father and had her memory wiped. Bo is struggling with the choices she thinks she made while on the Death Train and Mary has sage advice for the fae she raised. There is some conflict during the episode as Mary at first is appalled at Bo's place and the danger she puts herself in on a daily basis, but she comes to understand that Bo is more than capable of handling herself and at the end tells Bo that she sold the house and plans on traveling the world. Just as we think Mary is about to ride off into the sunset with her happy ending, Vex walks into the Dal and Mary recognizes him. But Vex does not remember her. He's confused by the terror on her face and Bo finally calms her down enough to tell her why she is so upset. And that is when we find out that it was Vex that was sent to town after Bo accidentally killed Kyle. And it was Vex that spent months tormenting both Mary and her husband until he forced Mary to kill Sam herself.

Things are about to get bad for the mesmer. Very bad indeed.