There is no such thing as a stolen best friend. Your friend could have another relationship that is making you feel like you’re missing out but no one can steal what’s already solid.
This principle applies to romantic relationships as well. Your friend could be growing in ways you aren’t. Whomever she is hanging out with appeals to the new growth. Her going out with other people is called life. No one can be so bound to one person that they can’t branch out and have other interests. You need to deal with your feelings and how it makes you feel. Drake says “no new friends” but the truth is although the new relationship may not ever get to the same status as you and her, the truth of the matter she can and will have other people she will gravitate towards that isn’t you!
Once you deal with your feeling surrounding how you feel you can make the time with your best friend more meaningful. You don’t have to compete with the new friend. You have an established bond like a sisterhood. You are still besties. Your friend has a new friend and it’s okay unless the new friend is a bad influence. If you can’t see a reason outside of she just shouldn’t be, deal with you so you can keep your friendship in tact and not come off as jealous! Nothing is worse than dealing with a friend that is jealous. It turns them into a mean spirited friend and that’s not something you want to be!