I might fired employee in a wrong way

I am the owner of the daycare and it’s a s Corp. I hired someone and she has worked for me for one week. I asked her prior to the interview how her health is. Because the day care needs sufficient number of teacher daily I can’t have someone who takes days off often. She wrote back to me that her health is good and she doesn’t take sick days. And she also told me she is certified special education teacher which I never verified because I don’t need any certified teacher. Anyway, in a week I had too complaints from our client that the diaper were put backwards. It’s not like someone who experienced do. Also today she took a day off by being sick. My other employee told me that she told her that she has an asthma and get sick very easily. So I sent a text saying that I don’t think she is a right fit for us. And I am not comfortable trusting her. And said please let me terminate as of last Friday. She saying that she will sue me because I fired her for having asthma. Also I paid her cash