What platform would you reach out to her on? If she was down to sell her feet pics, I doubt she'd have a problem selling you hers if you told her you wanted some. Just be straight up with her.
She's comfortable talking about her feet and showing you. It sounds like she would keep it between the both of you. You should definitely make the move and let her know you like her feet then go from there.
She does, he provided a short story on how it came about. (no pun intended lol)
https://footfetishforum.com/threads/my-mom-feet.24911/reply?quote=122151