A little confused 😳😕

My boyfriend is 26 and has a 10 year old sister. We are expecting a baby boy in the next 8 or 9 week's give or take. Well sometimes he will come visit her outta town and everytime she has been very nice to me and over all just a sweet girl. Well as I'm typing this, we got to her house about 30 minutes ago or so and when I walked in the door she gave him a big hug and had a huge smile on her face but when I went to hug her like I always have, she gave me the side eye and just have been different with me this time. I'm feeling a little uncomfortable here right now. Well after about 20 minutes of being here, my boyfriend comes and sits beside me and he says "go sit with her" (talking about sitting near me) she then says "... no I'm gonna sit over here" again that made me feel a little confused because she's always so quick to run and sit near me... My boyfriend ask me "is he kicking right now?" And puts his hand out to try touching my stomach, I quickly push his hand away and tell him "no, the baby is sleep" which he's not he's been kicking ALL DAY I just didn't want him touching me because his sister just kept giving me a funny look. I don't know what's going on with her but it didn't seem normal