How to prepare (rescue) puppy for first vacation?

That's great that she's going to be with people she knows in a familiar place and you're providing comfort items along with the essentials. If the foster parents are willing, maybe you can arrange to go there for some shorter visits before the trip (maybe just have a walk or play time together, then next time maybe leave puppy for only an hour or two, then maybe one more time leave for a few hours, so she understands you keep returning and this is her home away from home)

Skype! Try it!

Dogs are pretty resilient. If the dog was happy with her foster family until she became your baby, I feel she will be just fine with them. She's going to miss you no matter what but after a day she will settle and they will give her plenty of snuggles.

I think the clothes that smell like you will really help. I'd suggest calling those who are watching so she can hear your voice. My fiance does that sometimes and our pets can hear him when he's away. Even if they can't comprehend you in 2d form on a phone screen, I would think the sound of your voice would help.

Agreed with the other answers. I sat a newly adopted dog and his owner was worried that he'd have some separation anxiety issues. To address it, we had a long meetngreet, followed it with a daycare, and then a trial one night. As her pup felt more and more comfortable, we extended the length he spent away from her and it worked great! I also suggested she leave a blanket or shirt with her scent on it to comfort him while she's away. He did amazing, and we had a great time hanging out together :)