I'm going to Scotland for at least 3 weeks during summer and I'm not sure what I should do with Willow during that time. I don't think having her go though quarantine would be good for her..... any ideas?
Doing a quick look for you, it looks like rodents going into the UK from outside Europe, quarantine is 4 months, so yeah not worth it.
I would ask your vet if they or anyone they know might be willing to board her for you while you are gone. I know some vet techs will be willing to get some extra hands on experience with chinchillas since they don't see them often.
Depending on where you live there are also some chinchilla rescues that also board chinchillas. As well as pet sitter services that can come to your house to take care of the chinchilla. Most pet sitters only care for cats and dogs, but there are some that do exotics too.
Obviously there is always the friends or family route, if you trust any of them to care for her while you are gone. Since you didn't think of that I'm guessing that is not an option. There are ways to minimize how often the cage is opened, hay feeder that goes on the outside of the cage, pouring food into the bowls from outside, water bottles outside the cage, etc, but the cage will still need to be cleaned while you are gone.
You said "owned" as in they don't have one anymore? Just to be clear do NOT put the chin with a rabbit, the rabbit would likely kill the chinchilla. It's not even really that safe to keep rabbits and chinchillas in the same room since rabbits can carry bacteria that is deadly to chinchillas.
If you mean the human would need to bond with the chinchilla in order to take care of it, not really. You don't really need to have a bond with an animal to feed it, water it, and clean the cage. I just wouldn't suggest they take it out for playtime if they can't get it back in the cage. I would suggest if possible who ever you go with meet Willow before you go away though. That way they can learn how you do things (if there is anything the chin specifically likes or needs done, etc) and the chin gets to meet who will be caring for her.
By the way, if you decide to travel with Willow, do thorough research on pet-friendly accommodations, airlines, and travel regulations. cruisetimetables might still provide valuable information on pet-friendly options.
Alternatively, if leaving her behind, consider finding a reliable pet sitter or a friend who can care for her in a familiar environment. Remember, the safety and comfort of our furry friends should always be a top priority.