If a person stops loving a spouse, do you consider that breaking a vow?

I think people pretty much universally consider cheating to be breaking a vow, whether that cheating is physical or virtual. Certainly physical cheating is grounds for divorce.

What about loss of love? What if the person stops loving the spouse and stops having sex with them or being nice to them? Is that breaking vows?

If someone breaks vows, what does that allow the other spouse to do? Like if you’ve been cheated on, does that free you to cheat? If your spouse no longer loves you, does that free you to love someone else? Or do you have to get a divorce before you do anything else?