^ I do freelancing on friends. I charge them the same as I would anyone else. They call and make an appointment, we consult over the phone, I name the price.
The only exception is if we are planning a day to hang out and we choose together to do makeup as a fun thing, obviously then we are exercising the friend relationship and I don't mind playing with the makeups for free. I would charge her the same as you could any other bride, based on your skills and your expectation to complete what is asked of you. I haven't done weddings but I'm sure its not the easiest thing (you're doing multiple people in most likely a short amount of time), so don't under charge - you will be using a lot of product, keep that in mind. Research other MUA's in your area and see what they are charging as a going rate, that will be a good indicator of how much you should be charging. Also, keep yourself brushed up on the proper ways to sanitize products between clients. Good look!