Dealing with Overbearing Mother

Not sure if anyone here has experience with this or can just give some good advice....

I am well into my 30's. My mother and I talk a lot and are close. We live a little less than an hour away. She does not come to visit much, but I do go over and see her. She always wants to help, but sometimes it seems a bit controlling. For instance, she is butting into my relationship and decisions surrounding whether to live with my boyfriend or not (she isn't against it morally and does feel he is a nice guy). She'll get mad if I disagree with her opinion on life decisions like this one and says she won't help me again, although I do not rely on her financially, do not need to, and haven't for years. She says she gives me advice on things like this because she cares and does not want me to make a mistake, but this is too much at my age.

It shouldn't bother me, but it does. I've tried to tell her that I'd appreciate if she stays out of things, but it does not seem to work. How can I set better boundaries, and how do I deal with having a mom who wants to be involved in everything all the time? I want to have a good relationship with her and do not want to cut her off.