Should I send this letter? Advice, please?

Usually, I don't have a lot of problems with my mom, but this time it runs way deeper. I am deathly allergic to cats. And I mean, I break out in hives and have asthma attacks. In fact, recently, I had an asthma attack because of the amount cats we have in our house. My mom is a huge cat person, and I hate cats--which I think I have every right to. When I was little, she used to take me to allergy doctors, and she would always get me tested like she hoped I wasn't allergic to cats anymore. Always, I would end up showing I was once again allergic. Every doctor we go to and tells her that she needs to get rid of the cats, we never go back. To explain my frustration, we have four indoor cats. All that I am extremely allergic to and are all long-haired. Every time I tell my mom, she tells me not to start, that if I was so allergic to cats, then I must be allergic to my dog, too. I've let her get away with that excuse. I have a chihuahua that I have no allergic reactions to. In fact, I recently got tested this year, and it didn't show up that I was allergic to dogs, but still cats extremely. Before, all the doctors have said that I barely show I am allergic, like not really even enough to count, but they're under regulations to tell us anyway. My mom uses that as an excuse, but now she can't use it. Every time I've tried to talk to her about it calmly and ask her to only let there be one indoor cat, and let the rest be outdoor she tells me not to start. Honestly, the reason why I hate cats so much is because of her. When I look at one of the four that we have, I see it as a symbol that she is constantly choosing them over me. It's gotten to the point where I have this bubbling anger, and I am afraid I am going to snap soon. I mean, she is constantly choosing the cats over me. I have asthma attacks, and she just blows them off. The doctors have told her I have allergy-related asthma and it comes from the cats that I am allergic to, but of course, we never go back. I'm tired of this. I want to send her a letter so she can't interrupt me. This is serious, so no, "you're being a baby about this", because I am not. My mom will not listen to me, and she is risking my health over it. I am not joking. One time, I actually almost died of an asthma attack because she brought in a new cat that I was allergic to. I've tried to reason with her in the past. Even though I have every right to demand that she take them to a home where they don't have anyone allergic to them. I can't stand it anymore. I've been sick three weeks with this asthma attack because of a new cat we got. She told me it would be outdoor, but now she lets it in all of the time. She always keeps telling me that she'll make it outdoor, but every time I come home from school, there it is. I don't need the stress of my asthma. I am planning to send her a letter so she can't blow me off in mid-sentence. I plan to give her an ultimatum. I'm done and I am tired of trying to be fair and calm in the past. This is me or the cats, and it sounds ridiculous, but it really isn't. This hasn't been just five years of this. Ever since I was born, I've had trouble with my asthma because of the cats she brings in. She won't stop. And my dad won't stick up for me, because he tells me it's her only "solace" in life. I am her daughter. Does there really need to be a decision, because it always seems like it's the question to life here. I am just wondering if I should really send this letter--and I mean not just write it out and leave it alone. I mean, send it to her. Or try to talk to her again...? I've tried thousands of time, and the only thing that seems that might work is sending her a letter. If she keeps the cats all indoor, then I'll know that I just need to cut her out of my life. Today, she came in my room to use the computer for college work that I have been more than happy to let her use, but I found a cat that I am extremely allergic to sleeping on my bed. I now have to STRIP everything and wash it, or I could have another asthma attack. I'm not exaggerating.