XBT or other experts: 485 to be ted soon. Question for my Fiance

485 will be filed soon. Fiance is studying in Canada. Since we are not married yet, she needs to apply travel visa to USA so we can get married.

1) What reason will be the best and more reasonable to succeed in obtaining the travel visa?

2) If she comes here and we get married, can she stay here once I filed H-4 immediately? Where can I find the H-4 document etc. online?

Thanks a lot!