I have told my husband it makes me very uncomfortable and that it almost seems she attends hoping to run into him. Why else would she?
Would someone explain what the part in bold means please?
This is a more-or-less idiomatic construct. Why else would she? should be interpreted as What other reason (besides ...) is there for her to ... - in this case, What other reason (besides hoping to run into him) is there for her to attend?. Note that this is referring to an action and associated reason identified in the previous sentence: I have told my husband it makes me very uncomfortable and that it almost seems she attends hoping to run into him.