Good question @Wilyum. Im assuming you have already engaged her & paid some lil dowry to be given a go ahead by her folks for the wedding.
If that's the case, sit down with your madam,be open to her and with each other and explore the options available for raising cash to foot the wedding bill. You'll be surprised how easy it can be if you involve her completely.She'll support you completely & stand by you.....again,only if you involve her(open up to her)....otherwise known as project kufungua roho

Final thing...involve your family,your siblings first,your relatives second...then your friends....in that order! They say blood is thicker than water!
@SufficientlyP