I have contact with the Hanoi Disabled Women's Association - not so much a charity as a self-help group, but I'm sure they could use some funds in a valuable way. They have recently been providing training for disabled women home-traders (not just in Hanoi, but surrounds) in business skills so they can improve their incomes. Let me know if you'd like an introduction.

I would also recommend Blue Dragon Children's Foundation. They have specific programmes for girls, and I'm sure they would commit to spending all the money on girls if that's what you wanted. They're listed on New Hanoian.