Hi Sheba,
Wow, that's alot on your plate! I have a Mom like that, it's hard to get her to say she's wrong. She has gotten better with age and does so more than she used to. It's so difficult to get your parents to consider you an adult. Even as old as I am, I find that my parents do not always view me as an adult. I must assert that to them. They are ok with it now, but it's been a long road.
Many people/parents are like this, they wear blinders to their own contrbution to issues and it's easier to blame someone or something else. I guess what I'm trying to say is keep with it - keep reminding them of your adult status, your ability to make your own decisions for your own reasons. Remind them that you are aware that they may not always agree, but that it will not always be a reason for you to change your mind. You will only decide differently when you have a good reason to do so which doesn't include being bullied into it. You might also want to remind them that your boyfriend and best friend are your choice and not theirs. It is easy for your Mom to blame them because they is not blood related to her. This way she can pass the fact that you're "not listening" to her on them. Explain that by being negative about them, they are being negative about you.
The only words of caution I will give you is that you do need to consider what they are saying and search for any truth there, it would be a shame to throw away really good advice just because you're tired of listening. I think they're too controlling, but that does not mean they are trying to hurt you. Be open to suggestion, but don't be bullied. Hope it helps, but understand it's really easy to write and tough to do.
Keep with it Sheba, any chance you'll be able to get away soon? It sounds like you need a break from "the folks".