Best friend feeling left out?

Look, it's awesome that you want to make her feel comfortable, but you can't just not live your desired life and be happy in a relationship just because she's single.

"Never set yourself on fire to keep someone else warm; the warmth is only temporary until you disintegrate into a pile of ashes."

If she were in a relationship, she'd likely do the same thing. If she is truly your friend, she'll understand.

I would do this: schedule specific times on the vacation (not too long: 30 mins max) to talk with your boyfriend. That way, if she feels uncomfortable, one of you can leave the room or she can put on headphones for that time. Outside of those times, hang out with her and have fun being besties. That way you are not neglecting anybody, including yourself.

She is being left out. Maybe you can dial down the amount of time you spend on FaceTime with the bF while you are on a vacation with her. This isn't really about being single or not. It's about being good company.

Do you really need to talk to your boyfriend daily? Talk to him when you get home.

I would try to make an effort to only facetime your boyfriend when you aren't around her. Or go for a walk and talk with her instead for a night or two, but I'm sure she's fine and i'm sure she understands that your relationship is important to you.

Try to make some time with your boyfriend when you have your room to yourself. Try to keep it brief so that she can be in the room as well when she's ready. Don't facetime with him while she's there. That'll help her feel more comfortable about being in the room.