If there is love at first sight, how could a deal breaker change that?

People speak of chemistry, love at first sight and other such nonsense. Love is more of a foundation a relationship is built on. However, people say they have deal breakers, things that will not even get them to consider a relationship with another. If a man sees a woman, he is smitten, he gets to know her, ask her for a date, that leads to several dates, then an overnight and he finds out she snores and too aggressive in sex; two if his deal breakers. If he stopped seeing her, did he ever truly love her? A coed in college has the hots for the power forward with the Hollywood looks. She gets in his radar to the bane of all the other girls. On the 2nd date she ends up at his off campus apartment to discover he is a slob with a dog (no, she has no pet allergies); two deal breakers for her, if she really loved him, wouldn’t she try to find some middle ground or peace with it? If she say to herself she has to stop seeing him, if one can turn their love on and off like a faucet, was that really love?