You may know a little about changing pronouns. Many of you probably think it's dumb, but if you're reading this, I hope that means your mind is a little more open than that.
Use those pronouns chosen by the ones you love. You don't have to understand it, but you should try to be understanding. You may not agree with it, but you should respect it. Your loved one is counting on you to be a person they can trust. Don't betray that trust by writing off their feelings as a phase, a fad or a plea for attention. Don't make this about you. When someone you love wants to change pronouns, you do it.
I like to think of changing the use of pronouns the same way I think about a new pair of shoes. When you put them on for the first time after buying them, they may feel a little stiff. The material hasn't been stretched to fit your foot yet, and you're not used to moving in them. Give it time. The longer and more frequently you wear the shoes, the more comfortable they will become. The same goes for using pronouns you aren't used to. Give it time, and soon it will feel more comfortable.