My sister likes the taste of my cum

This wasn’t the first time and as we were living together I was really pissed that I was the one doing all the work out slide and in the house. I don’t remember how it came to it but I remember making her a coffee one day and just deciding that I’d cum in it to get back at her.

It felt like a great idea at the time so I took a mug to my room and jerked off until I came in it. I then went back to the kitchen and made her a coffee as I normally would, stirring my jizz into it until it dissolved. I then served it to her and was already planning on my excuses on why it tasted different if she didn’t like it but I left it with her. A while later she came to me and said it tasted really good and much better than it normally does so I said I bought new stuff so it must be that.

I don’t know why but this made me feel real empowered, I’d given her my cum to drink and she loved it. I carried on doing this and I feel really bad now every time I stroke into the cup and take back a fully drunk one from her so I really don’t know what to do. It’s gotten to the point where I stopped doing this and she actually complained at me changing the coffee we got “cos I knew she liked it” so I feel like I need to keep doing it, although it does give me a kick every time I’m doing it, it’s just the afterthought that makes me feel awful.

I’m after genuine advice on this btw on what to do.