Part fantasy, part question.

For a few years now me and one of my ex's have been fuck buddies in-between relationships. She loves ves being tied up and used as a sex toy and I love using her that way.

A little over a year ago her daughter turned 19 and about a month after she accidentally walked in on us. It made us all a little embarrassed at the time, but I haven't thought about it since.

Recently I got a txt from an unknown number, saying it was my ex's daughter and she wanted to talk. I didn't believe it at first so she sent a selfie of her standing behind her mum. Ok I say, how did you get my number and what would you like to talk about. Thinking she want help with her mum or something.

She got my number from one of her mum mates, but didn't say witch one. And what a surprise I got next. She goes on to say she's 20 now and can't stop thinking about the time she walk in on me and my ex, about how I made her mum scream and moan. And she wanted to talk about it.

A trip to Costa later I find out she's been getting of to the memory and has dumped lads because they couldn't do to her what I did for her mum. And she learned just what it was me and her mum got up too.

Over the weekend just gone I got another txt from her saying her and my ex have had massive argument, she's been even more turned on by what we talked about and that she wants to be my toy as well to get back at her mum.

I might have been down for it if it was just her wanting it, but I'm not sure if I should if she's doing it to get back at her mum.

What do you all think ?