@Mizchelle,
I'm sorry to hear your family/friends haven't been supportive of your decision to donate. Like others have said, family donations can be difficult because a lot of other issues can bubble to the surface. Not to mention that guilty, fear, anxiety, lack of knowledge/understanding can manifest in harsh words and behavior.
I donated to my mother too, 3 years ago; I was 27 at the time. I wouldn't say my family was unsupportive, but I know my mom had a difficult time with it. For the longest time, she didn't even mention the word "transplant" or present it as an option or possibility after she got sick. I was the one who kind of pushed more to learn more information. I don't think she wanted to ask, whatever the reason may have been. In the end, it turned out fine.
If you're truly comfortable with your decision, I think you should go ahead and do what you think is right. It may help to speak with the social worker at your transplant center, just to "vent" in a safe place. Or, if you're willing to speak further (or write a letter, whatever works) to your family and friends it might be helpful to talk them through your decision and provide them with links to more information about the donation process. In my experience, lack of information and understanding can cause a lot of angst or anxiety. But if that doesn't work out, then just do what you do, and it's great you have a supportive friend in your corner to back you up.
I know your donation is around the corner, so this could be a late post, but I could relate a bit so I just wanted to say "hi" and "good luck"! I'll be thinking of you. Take care.