I can't answer for you why you feel guilty. I can say why I would feel guilty if I were in a similar situation.
I would have felt guilty because I was still married to the man and my personal standards say no new relationship until I was divorced. Eve then appearnece of involvement with a new man would have felt wrong to me. And I had to deal with my own issues. I've been gone more than a year and a half, divorced for 6 months and still haven't even considered dating because I know I am not ready to jump into another relationship because I have my own self to look at and heal.