This link has a lot of good info:
ASPCA | How Will Spaying Change My Dog?
Princess & Turbo (sister & brother) got fixed @ 6 months of age. I wanted to wait til 7, closer to 8 months, but my friend that was taking care of them @ the time wanted it done asap bc Turbo was trying to hump Princess.
I think it was a dominance thing than a sexual thing loll but she didn't want to chance it.
Most Yorkies sexually mature around 8 months-1 year of age...but all dogs are different. To be on the safe side, maybe you can spay Maggie around 6-7 months, also have any retained puppy teeth removed @ the same time so she doesn't need to go under again. Meanwhile, play tug of war & it will help loosen loose teeth!