I have Muscovy and they make wonderful pets. Some like to eat them too. But I could never eat mine they are just too precious. My Muscovy drakes weights around 12lbs so probably not too far off of a Jumbo Pekin and his female Muscovy are anywhere from 4-5lb each they are tough ladies. lol
So sweet of you to take her in and give her a home.
I'd clip one of her wings to keep her home though. That maybe why she was hanging around at a person's home who didn't know her she could have been someone's pet and she flew, they do love to fly and can get lost easily that is how they end up in lakes ponds and other bodies of water. I only clip one wing on my girls each fall after their big molt. I can give you a diagram on how to do it if you want.
Most will say Muscovy need their own kind to be happy but I have one females Muscovy who I gave Runner /Buff eggs to back in 2016 and since she hatched those ducklings she has been part of their flock. I guess she must be able to communicate pretty well to be with them this long.
Any questions just ask. Many of us have Muscovy and love to talk about them. And of course the other breed we have too.