Help! What do I do if I feel like my boyfriend's mother causes problems in our relationship?

I'm 28 years old and so is my boyfriend. We are getting married in July and just recently I found out that my boyfriend's mother doesn't care too much for me. Along the way I had my doubts of her not liking me, but now I really feel like she doesn't. Me and her were emailing back and forth one day about a bridal shower and how I miss my him not being around so much. He moved to a new town back in Dec. to start a job so he only lives about an hour away now, but I was telling her how I worry about things and how I miss him a lot since he is away. Well we emailed back and forth and at one point I received an email from her where it looked like she had been writing back and forth to her sister Donna about me. In it, it said that I was messing with her son and that she didn't know about me. Also she stated to her that she had sent me an email that was kind of mean and that she didn't care if it upset me or not. After reading this I wrote back and told her that I didn't think I was supposed to receive that email. Then it took her several hours to write back and when she did she said nothing was said in those emails that hasn't been said before. Then she stated that someone had been getting in and out of her email account and she didn't know how I received those emails. So I tried to let it go and even write her back and act as if nothing happened, but then when I went to send an email I couldn't. I received an error message about an incorrect email address. Well later that day I talked to my boyfriend and told him of the mean email that his mom sent and he said he would talk to her about it. I was so hurt after reading I was messing with her son and that she didn't know about me. I never expected anything like this from her, but along the way I have always been so worried or scared that she didn't like me. At that point it was clear to me that she didn't if she was writing things like this to her sister about me. So my boyfriend tried to talk to his mom about the mean email I received and he wasn't mean to her in any way, but he told her he kind of thought the email was mean in a way towards me. At this point she gets all upset with him since he disagreed with her so she yells, then his father gets on the phone and yells at him. His father tells him he isn't helping out in any way with our wedding plans/the reception hall and then he hangs up on him. His parents were going to help pay for part of the reception hall for our wedding. So after this happened several days later my boyfriend is talking to his mom and father again like nothing happened. I understand because they are his parents, but just because they are his parents doesn't make the things they do and say right. All because he disagreed with his mom on the email being mean they canceled on our reception hall. From this point forward it really bothered me that he could just let this go with them and allow his mother to think that her email wasn't mean. I know he got into a little argument about it with both of them, but they acted as if everything was okay between them. I could not forgive my parents if they ever did that to me with my wedding. Especially if they did it just because we disagreed upon something like a mean email. I was really aggravated, hurt, and frustrated after all of this happened so I decided to write his mom and tell her exactly what I think of her and her behavior. All this time that I have dated her son she has always been fairly nice to me, but along the way she has always made little comments or jokes to get at me in some sort of way. So I wrote to her about things that she has said and done, her behavior with her two sons, and how she feels about them both having girlfriends. My boyfriend has a twin brother Tyler who also has a girlfriend. Anyways their mom hates Tyler's girlfriend and it's all over nonsense. She hates the girl because she stays at her son's home and she disagrees with the whole before marriage. Although she doesn't go to church or anything like that. With her hating his girlfriend it all started with us going on a vacation trip together. We went on a trip and me and Tyler's girlfriend had our own separate room from the guys. Well Amy fell asleep watching tv in the floor with Tyler and their mom flipped out over it. Her behavior over that ruined the rest of the trip and no one really talked to one another after that night. I know it was disrespectful for the girl to fall asleep in the floor because we did have our own beds, but they were fully clothed and sleeping with the tv/lights on. Also I felt like if the mom was really upset it should have been more of a problem to talk to with her son rather than to take it out on the girl. Anyways this whole time the mother has continued to hate Tyler's girlfriend for things that really don't make sense. I know she gets upset because the girl stays up at her son's house, but shouldn't she be gettiing upset with her son and n