To my best friend's boyfriend,

She's the person I crawl into bed with when I just need a good cry, she's the one I sneak out to IHOP with at 3 a.m. when I can't sleep, she's the one who will never judge me, she's the one I know would help hide the body, she's my person, my best friend. But she's also your person, your best friend, and the one you go to; you're her boyfriend. There's no reason we both can't have her and share her because it's going to happen anyway and you don't really get a say in it (sorry not sorry). You're basically dating both of us, I'm just more of the emotional support, but it's something you should get used to (me being around all the time, that is).

I'm the one that will be there when/if things crash and burn, and if they don't ... I'll be the bridesmaid in your wedding, I'll be your child's godmother, and I will be your savior when she gets too annoying to be around. I'll be your savior when she's over reacting to something stupid you probably did and I will calm her down and help her realize she's overreacting. We're way too comfortable around each other so I'm not scared to tell her when she's being a bitch, or when she's wrong, or to challenge her without making it a fight. So I hope you don't mind when I'm crawling into bed with you guys at 8 a.m. just to cuddle and hear about your night (I know you secretly love it), or when she openly asks me a sex question in front of you – no, it doesn't put me in an uncomfortable position because she was going to ask me later and tell you my answer anyways. And don't get mad if you pass out early and we go on late night adventures – you snooze you lose! The invite is always there, so no reason to feel left out.

But don't get too ahead of yourself, I can also make sure things go terribly wrong. My opinion to my best friend is important, and my approval even more so than my opinion. My advice? Stay on my good side, because if she loves you, I probably do too and I would hate to see two relationships go down the drain (yours and hers and mine and yours that is). My best friend has good judgment of character and that's probably why I value her friendship as much as I do, but I also learned from the best how to be a bitch, and how to make sure someone regrets the actions they take on others. Bottom line: do not hurt her and your body won't be the one she's helping me hide. Just don't hurt her.

Your girlfriend is basically my sister and not a day goes by that we don't live up to that label either. We fight about clothes, we tell each other the way it is, but we're also – without a doubt – there for each other through anything. No matter how close you two get, I'll still be her girlfriend and her person and I hope you can understand that.

Sincerely,

Your girlfriend's best friend, sister, and partner in crime