This is very difficult of not impossible. Remember women are like possessions here, she needs permission from her father and also the government as she is under 30 that is extremely unlikely.

The only way you can do it is if she leaves Qatar and never comes back. This means she has to give up her family and that's a hard thing to do.

If you so manage to get married any kids your have will never be Qatari citizens as it stands now as she is a woman, not a man.

However if you wanted to marry a Qatari man and you are a foreign woman then that is easy, they have no restrictions.