Boyfriends Mother Doesn't Like Me Need Advice On what to do

One of my friends suggested I bring this to you guys, so here goes nothing.

This is going to be fairly long and I apologize for the length but I need some advice from you guys. I've debated posting this for a while but I'm at my wits end and need another perspective.

"My boyfriend and I have been together for 1.5 years. In love, support each other, he's my best friend, the whole 9 yards. But his mom doesn't like me and I don't know why.

Let me preface this by saying he is the youngest of his 4 brothers in a bilingual family with extremely religious (7th day adventist) parents and before me, didn't date anyone for the better part of 7 years. The first time I met his family was 4 months in and it was a lunch at his parents house 2 hours away, we weren't living together at the time but we met at work. My boyfriend invited me and I was excited to meet his family because I'm a family oriented person. At the house, his mom spoke to everyone in Spanish at the table (which I can't understand) even though everyone knew how to speak english. I started to feel a little left out and uncomfortable but I brushed it off when we left.

Fast forward a month or so and he invites me to his grandpa's nursing home to celebrate grandpas birthday. As my boyfriend was introducing me to his grandpa as his girlfriend, his mom loudly interrupts him in perfect English to say that I am his "friend". I got pretty annoyed and walked outside to cool off, my boyfriend followed me and I asked him why she did that. He gave some bullshit excuse like his grandpa is "old fashioned" or some shit like that and I started to argue but I dropped it because his family was around. We leave shortly after.

We move in at the 7 month mark, we loved each other and it was financially a better decision anyway, Cali isn't cheap. One day as we are carpooling from work, he gets a call from his mom that her and his dad are in the area and invite him to lunch. He asks me to go with him and I flat out refuse and i offer to drop him off instead and go home because his mom makes me feel nonexistent. He starts begging me and i finally agree despite my hesitation.

This is the incident that has eaten me alive ever since. They were about to check out a nearby museum so we met up with them there. They were waiting at the entrance. I say hello and she mutters something and I knew this was going to be super awkward. They all start talking in Spanish, once again making me feel left out. I go to the bathroom to avoid the awkwardness and upon my return, his mom immediately says to me (I shit you not these were her exact words) "Can you go away? I want to talk to my son." I was taken aback by it and I say OK and put my hands up and start to walk away to the car. Behind me I hear my boyfriend say, "you can't talk to her like that, she's my girlfriend, whatever you can say to me you can say in front of her." Boyfriend chases after me which causes her to chase after HIM and all the while she is screaming things like "She is not apart of our family!" And things similar to that. I reach the passenger side of the car and as I'm getting in she starts to come at me and my boyfriend is blocking her from getting in my face. To this day I have no idea what her intentions were. They start arguing in Spanish to each other and she's like "Let me talk to her, let me talk to her" and I'm just bawling in the car. I scream, "I don't understand why you don't like me" and she responds with "Its not that I don't like you or do like you, it just... it is what it is!" Boyfriend closes my door and gets in the driver's seat, his mom starts crying and tries pulling him out physically and my boyfriend says "This is my girlfriend and I love her and you can't do this" and his mom accuses me of stealing her son away from her and we eventually leave, me bawling and my boyfriend astounded. It was a traumatic and humiliating experience for me and I blocked a lot of it from my memory.

You can say that my boyfriend defending me was awesome. But, the next day, they started texting and talking like nothing ever happened. I PESTER him for months and months to talk to his mom about me and that incident but he never brings it up and avoids it like the plague. His excuse? He doesn't like confrontation.

One day I go through his phone (stupid I know) and i see a text message from his mom. It was half in English so I put it in Google translate. The translation? "Don't tell anyone you're shacking up with your friend, it's very shameful". He doesn't acknowledge the comment at all and instead changes the subject. I get super heated but I just internalize it and later blew up at him about it.

I'm at the point where I'm considering breaking up with him over the lack of acceptance from his family. He always says he will talk to her but never does. I start feelling immense guilt because he chooses to spend time and holidays with me and it makes me feel like shit because i dont get invited to anything and we havent bothered visiting his family together ever since. I gave him an ultimatum a couple months back and he STILL hasn't talked to her about our relationship.

I finally got fed up and took matters into my own hands. I wrote a 4.5 page letter a year after "the incident " talking about how much my boyfriend and I love and support each other. I tell her about how much she hurt me with her words. I tell her that her son chooses to spend time with me and that i never "took him away". I tell her she knows literally NOTHING about me and plead to know why she dislikes me so much. I bring up the text message and say that I am a human being with feelings and that it hurt me immensely. I write about a lot of things and send the letter, which i debated sending for hours. It has been about 4 days and I'm so anxious, I haven't heard anything from my boyfriend at all whether she said anything to him or not. I decided if the response is negative, I can't go on with my boyfriend like this, with our relationship not being acknowledged by his family and being treated like a common prostitute."