great advice Murienn.
Since I lost my husband in July, I have gotten very active on a forum for widows.

The scenario you described does happen and it almost destroyed a marriage that i know of from someone on the forum.

a Woman died, his best friend's wife and widower got too close, etc...
and now this widower had to do the right thing and get away from the woman "who was only trying to help" but it was getting physical. The widower is doing better now, but he lost two friends.

good luck.