Welcome to our forum. Gosh, where to begin with your question. If you've read any part of this forum, you've probably discovered adding a new kitten goes well or it goes horribly wrong. You can find pictures online of cats grooming each other, sleeping together. That's the ideal situation.
The key will be in the introduction of the new kitten. Even if the kitten is a DSH and not of a specific breed, it is still important that the kitten have a safe room to decompress. Has this kitten been around other cats besides its mom and siblings? Has it been socialized with humans?
You know your bengal better than anyone else. Is she completely calm and laid back? Does she get agitated easily? Since she has been through several foster homes, it is possible she is not yet acclimated to her new life with you. Is your home catified with cat trees and lots of toys? Know you will need at least one more litter box.
Many cat owners feel their cat needs a companion, but does your cat want one? You would hope your girl would take a motherly approach to a new kitten -- maybe she had a litter or two previously.
As for adding a male or female kitten, I don't know that it matters at that point? They are just kittens. A male is going to be larger than your female more than likely and you would need to make sure he is neutered before he reaches sexual maturity. Same with a female kitten. But, the sex of a kitten is up to you. I would probably take a female, but that's just me. Unfortunately, I have two male cats -- a bengal and a DSH. Not what I wanted, but they found me so I have them.