I'm engaged and I think about another woman.
Why are you thinking about another woman when you are engaged?
I think she's better looking and has a lot of money.
You are being loyal to your fiance with this kind of thinking. She would be hurt to know that you are thinking about another woman.
She would get over it.
She might get over it some day but you aren't even sure if this other woman likes you or is in a relationship. You should be happy with your current relationship. It's wrong to try and betray someone you care about and who cares about you.