Bless your heart for wanting to take in Boo kitty! The absolute best thing would be for her to go where she knows, with her family but since that isn't an option the best thing is to make sure that someone is with her at least for a while. Loosing your mom was probibly a very traumatic experence for her and this wont be any different in her mind. Hopefully you will be able to make the transtion period for her as pleasant as possible. Keep in mind what she must be going through, and help as much as you can.

I wish you all the best and again bless you for taking Boo in!