Was/is my soon to be ex wife trying to set me up ?

I recently found out my wife is/was cheating on me with a an ex close friend of mine. She said only for a few months but I don’t believe it. It was a long time coming and she was acting different with with me.

I’m asking for advice due to some recent things and some past things about her older sister.

Her older sister who is 2 years older than her has been message via FB messenger asking me if I’m okay and that she fully supports my decision to divorce my wife. I thought she was just being nice until she offered to come to my house in case I needed to vent to someone.

Another thing, her sister stayed at my house a little while ago because her house was under remodeling. During her time, she was walking around in a towel putting lotion on in front of me. I didn’t think much of it but is my soon to be ex wife trying to get her sister to sleep with me ?

Her sister isn’t particularly attractive to me but maybe she told her sister she was having an affair and tried to get me to slip up with her sister then she won’t seem like the bad guy.

I just think it’s weird her sister would ask to see me during this time and even weirder she would walk around my house with nothing but a towel.

I’m not over thinking this am I ?