Having been involved with rescue, and having failed Fostering 101 each and every time, I understand a bit of what you are writing about!

Just remember, Maggie is not Alice, and she does not replace Alice. Maggie is Maggie, and she needs / wants to be loved as Maggie, for herself. Perhaps she does resemble Alice in many aspects of her personality, but she IS going to do something, some time, which will slap you in the face and say, HEY! THIS IS ME, MAGGIE!

If you can manage her financially, then go for it! She needs a home, and sometimes those who need a home don't wait for us in rescue to be ready, they need NOW. Finding one who fits in with a pack is a special sign. Sometimes we have to grieve one and express joy over a newbie all at the same time. NOT easy, but that's part of rescue.