Don't know if it counts, but I am pretty much a gurlfrand to some of my sisters/cousins.
And I tend to treat their friends the same, and the few friends I have of my own, the same as well. And as the dude above said, some are pretty much sisters/brothers(cuz why lock them into a age old concept, eh?)
Finding someone attractive and wanting to be with them are two entirely different things, or at least I have found it to be so thus far. I don't see anything different between either gender when it comes down to it, we are all pretty much the same in the end, with our own insecurities wishes and so on and so forth.
Just because you think someone is cute or even have a crush on them, doesn't mean a friendship is impossible, the crush may fade within months of knowing them, or they may just turn out to be assholes in general.
Think of it like this - there a LOT of cute people out there in both genders, so forget friendship for a second, they are gonna be there in your professional life, your family life, and other spaces too, so if you see them as a whole person who picks their nose like anyone else, it will be much more helpful.
What if you have a handsome/beautiful boss? You don't wanna stutter your way around them, even if they are understanding and utter badasses, it will impair communication and slow down the work, or they might fire you after a certain point.
No doubt, social anxiety and inexperience with people may make it initially harder to talk to them, the key is to stop locking them into the role of the gender you would like to get with someday, there a range of relations possible here.
Try to look past any appearances, creativity and imagination will help here, just imagine joking around with her about random things or discussing a common interest or just enjoying silent company or a hug or two, or a brofist when a favorite sports team scores. Or heck, even imagine an argument or something, hit each other with pillows or something and have another person separate you both and act as intermediary for the fight. Both genders can royally kick each other's behinds when it comes down to it.
Can also sometimes help with intrusive fantasies.
Also, start with older people perhaps.
I am much more or even completely open with the women in my life than I am with men, again, they are pretty much the same to me, but I suppose that comes down to having developed at least a slight distrust with most of em, I strive to keep my influences positive and there a lot of sexist asshats out there.
Hope that helps.