<human>: Throwaway because husband is a redditor, and I'm sorry in advance for how short this is. Husband and I have been married for 8 months. 

My SIL lived abroad while my husband and I dated, so while I knew they were close (they talked a lot), I never realized how close. When she moved home it became pretty clear. They're constantly talking, frequently visiting, and when they do visit, it's like I don't exist. It's all elaborate, obscure inside jokes, and "Oh my god, I was just going to say that! Stop reading my mind!" 

And when I try to get in on the fun, one of them will talk over the top of me, and then they're talking to each other again. When I leave the room they hardly notice. My husband won't even *look* at me when she's around. He said once that "No one will understand [him] like Emma does," (fake name used), and that "Emma is perfect. She will always be my best friend." 

Found out recently this is one of the reasons my husband's last serious girlfriend broke it off with him. It's pretty bad. 

Regardless, this problem has always felt pretty high school-ish to me, so most of the time I just keep my mouth shut and deal with it. After all, our relationship is great when Emma isn't around. Next week, though, we're going on vacation with his family (Emma included, obviously), and I realize I'm dreading it. I don't want to be a third wheel to my own husband for an entire week. 

My first thought was to just sit my husband down and talk about it, which I will probably end up doing, but I hate the idea of him forcing himself to interact with me when he really just wants to talk to his sister. 

It might also be that I'm blowing this out of proportion and shouldn't worry so much. I'm open to that possibility as well. 

What does Reddit think? Talk to my husband, or suck it up? Any and all advice is appreciated.

Can you condense the text into three sentences or less?
<bot>: My husband ignores me when he's with his BFF sister, and I'm worried about going on vacation with them. Am I overreacting?