That's not normal, but a lot of time children at the age of 2 or 3 get sick a lot. I persoanally think it's genetic, or they just didn't get enough breast milk to have a good solid immune system. If your boss fires this woemen and she has doctor bills etc to show where the kid is actually sick, your boss and be in hot water.
But being a sick child myself, I know how hard it was on my parents, and yes my mom had to take off work at times. What my parents did was work split shifts, one would work during the day the other the evening. So there was always someone home to take care of the sick kid. I don't know how sick this child is, but if it was like me and ended up in the hosptial 2 or 3 times a month it didn't matter what shift you worked, letting your child be alone in the hosptial is just plain stupid. As the doctors in the pediractics wards are over worked, so are the nurses, and mistakes are made. Especally if your not there to pay attention and catch them. Even when I broke my back 2 years ago I was really lucky to have my mother there, as even in the ICU they made mistakes, they gave me a medicine I was allergic to, even after it was on my chart, and one doctor had take it off the order, but hadn't competely put it into the system, so the next morning I was given the medicine I was allergic to. If the child is in the hospital you do have got to double check everything they bring in. As the doctor is to busy, the nurse is to busy, and no one checks with each other, and you got one going this way, and the other going this way, and someone who is not sick has got to be there and make them work together. So basically what I'm saying is if her child is in the hosptial, she really doesn't have a choice but to take off.
And also the daycare could be mostly at fault depending on what kind of infections, some day cares just don't follow the health regulations and keeping things clean, or not letting children to this or that. If you can you may want to help her find a diferent daycare, or maybe a stay at home babysitter that is qualified to take care of sick kids. As I hear about a daycare getting fined about every few months around here for not doing this or that to keep the children clean or safe. And on some things I'm sure the children have got to get sick from it. I remember one story, about a day care, that if your kid was considered potty trained and went in his pants, they'd let the kid walk around like that, until you got their and changed them. And either output left agaisnt a child's skin and burn and cause infection. Also if this day care allows other kids to mix with the sick kids it causes all sorts of problems, and if they allow kids in who haven't gotten their shots, it's nothing to see nearly all the kids be sick of some disease.
Personally if I was that kids mother and the kid seemed to be suddenly getting sick a lot after I put them in a day care, that kid would be out of that day care immedately. Granted I do know some people to believe that their kid should catch everything at a young age and then they won't be sick later. And will actually put them in places so they can catch this or that. I'm not one of those people who believe that, and personally couldn't wish a child sick like that.
Good luck, that's about all the advice I could give you, as I don't know what the excat situation is, I hope it's something simple as to find a different day care, or a day time babysitter. Or if it's possible her and hubby work split shifts until the kid gets past the sickness. But that's not always the easiest to do, and not all men are willing to take care of a sick child. Though I do hope something works out for her, that is a really tough spot to be in, especally when you have no control and just see your child get sick over and over again. Also tell her to start bringing in proof of her doctor bills for the child on the days she took off work. It's a lot harder to fire her, when she was at the doctors office with the kid, and the kid was actually ill. She can go to the labor board on your boss for that, and have a pretty good chance of winning, and he has to give her either pay or her job back. I was lucky my mother's boss questiooned her about the same thing, as she took off for a month while I had two major surgeries when I was a child, I was in the hosptial for the whole month and it was over 300 miles from the town we lived in. So it wasn't possible for her to drive to work, and then back to the hosptial. Just the women she work with convence her boss that I wasn't that sick and my mom just did it to get time off. He came over to our house to demand my mom to go to work, I was in the hospital bed that they had put in the living room, and he seen me after two major surgeries on my neck. I looked like I went threw the war and I had a helo brace on. Made him instantly sick when he seen me. He never questioned her again, when she told him I was sick. So if all else fails bring in the sick child, let it throw up on the boss, they are almost always more understanding when you tell them your kid is sick after that. As sometimes you really have to hit people over to head, to realize that life throws you a bad hand, it's not just make believe, that you have a sick child. As for some reason, some people think children don't get sick. That you just can't possibly have a sick child, and they won't believe it until it happens to them.
Good luck
Kit