My mom is driving me to the edge of insanity...

When I was 10, my parents separated because something went wrong with my mom and she completely refused to get help. While she's been here physically, she hasn't been the same in the head. She used to be this over the top religious person and then one day she just stopped all of it. Religion isn't the problem here, none of us are religious, but it was shocking to see a change like that from a woman who once was the way she used to be. She used to be this person who loved socializing with her family but over only a few days she's cut off her entire family, not including my brother and I. We're the only people in her phone conversations I've noticed and honestly as the days go by we're both growing sick of her because of how she's been acting toward us. She went from this loving, reliable person to a person who cares about no one and is completely loose in the head and none of us know what to do. I'm currently living with my dad and I have been for the past 3 years. I'm not being forced to visit her every other weekend, but I've felt like it's for the better and I've constantly tried to get to the bottom of what happened but it's been to no avail. After each visit, that "it's for the better" feeling is just drifting away. I'm fourteen years old and my brother is twenty two years old and my mom treats us like we're toddlers. She raises the pitch of her voice drastically when talking to us as if we're babies. She dumbs down words as if we can't comprehend full sentences. Like, she'll say "kissy" instead of kiss or "piggy" instead toe or "oinky" instead of nose. I know it doesn't even sound real, but it is and I get to live in it. It's DISGUSTING the way she talks to us. She talks to my brother the exact same way. She even goes as far as to referring to herself as "mommy" instead of using the word "I." She makes me want to rip my hair out every single time I see her and I don't know how much longer I can do this. I've tried to make her stop talking to me that way by giving her one word replies to see if she gets the hint to quit it, but it's like talking to a wall and she just does it even more. I called her one day and tried to calmly explain it to her, but she lost a grip and flipped out... she acted like I was the crazy one and that what she was doing was normal. Heads up: IT'S NOT and I KNOW it's not and I've reached my wits end at this point. For over a year, she made me believe I was mentally disabled as bad as that sounds. A few weeks ago, my brother's room mate (he has custody of, he is under 18) went missing. He just ran off. When my mom heard, she said something like "If I see him I'm gonna drag his ass into the back seat and fucking beat him the whole way there. WHAT WAS HE THINKING?" A few days ago, his body was found and he had killed himself. When my mom heard the news, she flipped out and showed NO sympathy. She was just completely dead centered on how hurt my brother must be and she showed pure hatred toward his poor roommate who she knew nothing about what he was going through. It's fine to be more centered on your kids, but are you kidding me? He'd died, for christs sake... I'm ashamed to be her daughter... Every time I go over, I just cry to myself at night. I miss her. I really do. I miss the past her. You can't even talk to her about problems you have with her because she's so stuck up that she believes she can do no wrong. I actually heard her say "This is my world and they're all just walking in it." She makes me sick to my stomach. If you say anything she disagrees with, she'll be obnoxious and say "no you don't." (e.g if you look at a dress in a store and compliment it and she hates it, she'll say "no you don't" as in "you don't actually like it"). She's extremely homophobic, too. When I was 12, I said to her one day, "I have a crush on this one girl at school" and she freaked out and started disgustingly saying "No you don't you're just CONFUSED" and proceeded to tell me that women couldn't like women as if she had ANY business being as ignorant as she was on the day I said that. Things are getting worse for my brother and I and I think we both deserve better than this. What do I even do? Should I just give up and stop going over?