how to have a hard/embarrassing conversation with my (24f) sister (25f)?

for context, i have a boyfriend of 5 years and we love each other very much, he is my first everything and generally we are each others best friends. i also have issues making friends, i am pretty shy and awkward.

my sister only recently moved to my town, and i was ecstatic since i finally had someone besides my bf to truly hang out with. she is my best friend, though ever since we were kids i kinda knew she doesn't act as if she ""respects"" me, like always telling my private things to others instantly. but i guess close siblings are often like that, and she is generally extremely nice.

she also has trouble finding friends like me and wants to come over practically all the time to our place, which i haven't minded much. but i guess i've started to feel stressed out whenever she is here. she gets more intense (if that makes sense) than usual, and only really refers to my bf, not me, making me feel excluded. plus it's not really like he can do much else when she's in his face yapping lol, she is very talkative these days and he has mentioned this stuff too.

it's not like it's wrong, but it feels like she is very intently trying to befriend him and is always in her people pleasing mode around him, i notice she tends to do that to men mostly. she also says things like "he feels like an actual visitor and you feel more like a roommate" while laughing. for extra context, she kinda brought up this topic on her own when when we had visited her and i stayed overnight. i felt a bit hurt by this roommate comment since i really only come over to her place once a week. she has mentioned she wants them to be friends since she has no friends, but i feel like it seems to come at my expense, idk how to put it better.

there are other things too, but it feels she often makes small jabs at me or talks about stuff between us two so i have to explain to everyone (such as suddenly mentioning i've been "avoiding" her in front of my bf when i had just invited her over/said yes to her wanting to come over less than usual one week). this mostly seems to happen when it's me, my bf, and her hanging out.

tl;dr i never feel stressed out when it's just me and my sister hanging out, but her behavior changes a little when we hang out at our place with my bf, and it makes me feel weird/stressed out. like making small jokes at my expense or only really focusing on talking to him.