How do I extend my fiancee's visa?

Greetings:
My fiancee arrived in Doha from Kuwait about 2 weeks ago. We want to get married in Qatar so she wants to stay in Qatar until we are married. She is a British national so when she arrived in Qatar, she automatically received an one month visa. We would like to extend her visa for at least six months if possible. Does anyone know the steps to do this in Doha? Any advice given is greatly appreciated.
So what 's the final plan ? .................
Jim, Congrats dear .......... Wish you joys ...... ! ...... Let her stay here for a month after that you travel to Kuwait for one month ....... then both of you return back to Qatar ......... this way you can stay together for as long as you both wish ... means full life ............
To marry you need RP and after Get married then apply for family rp.
I am assuming that since she obtained a visa on arrival, It is valid only for one month and cannot be extended.
Get married then apply for family rp.