Who are your options? What female relatives have you got?
For example, when I was younger I thought I'd have my three female cousins, but as it happens, over the years I've drifted apart from all of them except one, so I have absolutely no qualms in only asking her.
I think it's pretty normal to only have sisters, or if you've got any little girls in the family, (cousins, nieces, etc.) that could be nice too.