Please don't put off taking action. She's already in her second trimester and hasn't had prenatal care. It's going to snowball from here.
Go to the local Social Security office (if your husband is mobile and not working, have him go if he's able and if you can't take time off from work), with your daughter, and start the Medicaid application process. Bring her birth certificate and picture ID and bring a pad of paper and pen and prepare to take notes, and prepare to wait in line. If they turn you away, ask questions: where would you go for help? what office should we go to? what are our options? Stop thinking and reading and wondering, and GO.
Your husband receives disability payments, so he must know where the office is. He's been through the process of applying, so if he's able, get him to take over the application process. It's a matter of going to the Social Security office and requesting the paperwork and asking someone what the procedure is when a birth is approaching.
Then make sure she's taking prenatal vitamins. Ask a pharmacist for a recommendation.
If she knows who the father is, what responsibility is this boy taking, or his parents? Does he know about the pregnancy? Is he going to be helping to pay for expenses?
You have health care, and I assume your husband is in contact with a medical professional. So call your doctor's office, or go in person, and ask them what resources are available in your county for pregnant teens.
If your daughter plans to raise the baby, you're in for a lot of expenses, and the birth will happen whether or not you've planned for it, so have a good honest talk. Who will care for the baby when your daughter's at school?
In answer to your question 'does anyone know if she will get on Medicaid', YES. Someone knows. But each state/county is different. Please go to the Social Security office and start asking questions NOW, and find out what the process is.
As others have said, Planned Parenthood may also have resources. There may be informative pamphlets there about Medicaid, or preparing for a baby as a single mother, or getting the help you need. They also may give her an exam, although not all do.