The process of dating is to get to know one another more deeply. to see if the 2 can grow together in the same direction, etc with the direction towards marriage and commitment ( as I see it ). That is the time, during dating, prior to making a commitment, to change ones mind. It is not about being indecisive, it is about knowing what you want and what the Lord wants for you. People can become unattractive for a number of reasons- life direction, gender roles, careers, habits ( good or bad or both ), where they want to live, children and on and on. It can be tough but, if someone becomes unattractive during dating, that is the time to separate either for a bit to reevalutate, or to move on. It is better to be alone and available than to be with the wrong person. Because, that right person may come along and if you are involved with the wrong one, opportunity is lost.
I have had Gfs that became unattractive. We were not able to work out our differences and separated. We are not enemies. I wish her well and do no think seh hates me because of it. Maturity goes a long way. All this posts, of course, applies to being single. If one has made a commitment to marriage, than one must stay loyal and faithful in that marriage but, not during dating.