your best thinks probably that you and him/her wont spend time together like y'all use to before you get married.Also your best friend is like a big brother or sister that has to take care of you and lead you to the right path to your future.
Yes. It's a big decision that a woman makes, and for one of your so called "friends" says no and tries to stop you, that's wrong. It's not her choice, it's yours. And marriage is a great gift. Your "friend" needs to realize you'd be happy with your husband, and needs to stop being so jealous about it. Jealousy is wrong, and if I were you, I would completely ignore her and shut her out of my life.
She is more scared that her relationship with you will either be changed or even lost. It's totally understandable that she doesn't want to lose you. Talk to her tell her yes of course things will be changing but for the better and you will still be her friend no matter what!