Was I out of line?

My bf has a 3 yo son with his ex. In my opinion, she is very neglectful regarding the kids health. Since he and I moved in together, I've diagnosed this boy 3 times with 3 different illnesses that his mother said I was overreacting about. First time was an inner ear infection. Second time was asthma. Then I realized he has eczema as well. Since he has been diagnosed by a doc with asthma, and he has had a real bad cough lately I've asked her to take him to the doc. I would but I'm not his parent and my bf has taken him but at this time he can't get him to see his normal doc during the day as he works long hours. His mother has refused to take him no matter how concerned I seem. She came to pick him up today and I kind of went in on her but I didn't curse her out or anything. Just practically BEGGED her to take him because he's been up half the night. She got mad, said I should have taken him, then called me out of my name. I had an attitude, absolutely. But I don't deserve that for caring about her son. Am I wrong for being concerned? Should I just shut my mouth and let the kid be sick or what?