Hi Jayykayy and
Sorry you found us in this way. I think you could ask the rescue she came from anyway as they may well have a home lined up waiting for someone just like Molly. You can tell them she needs to stay with you until a home comes up, though? Then you effectively become her fostermum.
We got Sam this way - he was eight years old when we took him over, but his family had allowed him to stay with them until we came along, and he was advertised by the local rescue on the usual Catchat pages.
Please don't be too quick to reject this option, many cats are re-homed this way.
Meanwhile, try some pet allergy wipes on Molly and your baby (pets at Home do a very good one, on offer at the moment) , and around the home with Petalcleanse to minimise the allergens and make life more bearable for the humans involved.
Good luck - I wish you and Molly all success.