Most chins take at least a week to get to know new people, some times less but most times more, my current two they were good within hours of being here. If she is fine with handling with her current family it shouldn't take long to get use to you since the handling isn't new just the humans doing so. However some chins act completely different in a new home, or kind of freak out for awhile, especially if it's a new cage with new stuff since nothing smells like them. I wouldn't really use youtube as research material, people tend to do a lot of stupid and dangerous things that they then post videos of. For example feeding junk food, using run around balls (aka death balls), making their chin swim... the list goes on and on. This forum though is a great wealth of info, we have everything from pet owners to commercial/large scale breeders on here, so some people with decades of experience.
If you are taking about personality change at puberty, that normally happens around at roughly 6 months to a year, give or take a few months.
As said the fleece you'll want to change a couple times a week, it all depends on how much she pees and if she uses a litter pan to pee in or not. Don't use fabric softener or chemical detergent to wash them either, vinegar works well and is safe. Also another thing to mention with the fleece is if she chews it you'll have to remove it and use a different kind of bedding.