What is your boyfriend's take on this situation, hun? Is his mom notorious for being difficult?
This may just be a personality trait for her, and may not have anything at all to do with her feelings about you. I believe there is also a cultural aspect to her behaving this way, and as I understand it, she is acting the part of the matriarch. You are a sweet girl, and I think if you applied yourself to winning her over, you'd be able to. But yes, it will take a lot of effort. Your BF needs to be more proactive in setting actual TIMES for you to meet.
In the end, after exhausting every possible option, I suppose you could flat-out ask her what can be done to improve her feelings towards you.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?