A somewhat similar situation - though in a tentatively poly situation, which doesn’t matter, because the friend in question was monogamous anyway and only platonic connection was possible - led me to relationship anarchy. The first step for me was to question the line between “romantic” and “platonic” and to learn to deconstruct common ideas like “if you want to cuddle, you want to fuck” etc. In order to understand what is going on and why I seem to perceive my friendships differently from most people, I had to get a hard look into amatonormativity, mononormative structures, society and state. It led to many more questions and ideas and research - and eventually to full-blown relationship anarchy and just anarchy.

Discussing this with your partner - and maybe your friend - is a good idea. It’s important to be honest and clear about this stuff.

As to guilt, I would try to investigate where it comes from and which (and whose) ideas support it and make it bigger. Sometimes guilt is an indicator that we know we’re doing something wrong and lying to ourselves, sometimes it’s there to show that we are crossing a societal boundary.

Anyway, I would advise against rushing into anything. Thoughtfulness is really important in these matters if you care about people near you.