Did this teacher have every right to be harsh on these students?

I worked with special needs children after school and one of the ladies who I became friends with, she is such a sweetheart. One next day the kids in her group who have trouble with their numbers but they know most by now. They didn't count with her. She got upset. She said harshly, "You guys need to do your work. That was disappointing. That's probably why you can barely count because you don't know your numbers!! 10 year olds that barely know their numbers! You're not going to graduate if barley know how to count! Junk!" The lead teacher and I were shocked. I was like, "Jenny! That was harsh!" The lead teacher said, "Jenny I can't believe you said that to them!" Then Jenny said, "WELL they weren't saying it! They're not even trying hard enough! What else am I suppose to say to them!"
I couldn't believe her. She never said stuff like that before. She didn't seem sorry about it. I told her after work that was so messed up. She said, "Well if they actually tried hard enough I wouldn't have to say it. I have nothing to be sorry about! Truth hurts sometimes. That's the only way students can learn. She didn't care or seem to regret what she said. She was very tried and cranky. The students looked hurt and one was about to cry.
I reported her but the boss said I need to stop gossiping and sometimes tough love is the only way for kids to work harder. She was in the right. Off you go.