Am I right to be mad at her? /work related

I 21f have a 24f manager. I have four years of food experience and she had roughly six months of food experience before getting the manager position. Her mother has been the manager of a different department for years. The mother had gotten the daughter and another son both manager positions around the same time. I feel like the daughter would not had been even lightly considered if the mom wasn’t who she is in the store.

She has been a manager for quite a few months now but never a “good one”.

Now recently, my manager found out our fryer filter system was broken late at night the previous night. One person of night crew knew “roughly it was possibly broken” but it wasn’t his job to say anything nor was he the one to deal with it. He apologized for not telling us regardless. Manager hasn’t apologized.

When this happens we are suppose to close down the food area because if we can’t clean the oil, we can’t cook with the oil. It’s a health/safety risk. We believe she didn’t know this because she did not tell any of us to close down the food area the next day nor did she tell anyone on morning/afternoon crew about this problem.

I tried to filter the fryers the next morning and it malfunctioned due to the break and threw 300 degree oil on my leg. I luckily had baggy pants on that I was able to hold away from my leg so it only turned into a first degree burn but did result in me crying in the walk in with my pants half down shaking in pain. I ended up going to the er because we thought it was going to be worse. They told me my jeans honestly saved me from most of it and if I had skinny jeans on, it would’ve been worse.

Ever since I found out that my manager knew and neglected to us, I’ve been upset at her. This all could’ve been avoided if she simply told us. She didn’t follow any proper procedures and didn’t even have the knowledge to like she should’ve as manager.

Is it wrong to be upset with her? She couldn’t have known that it would throw oil on me but also she didn’t follow any of the proper steps. I didn’t like her before this and this definitely isn’t helping.

And yes, work is paying for my er trip. I had to see two doctors for their paperwork resulting in me having to drive around/be at the doctors for a total of five hours that day with my new burn and jump through many hoops with my work. It was all very frustrating and painful.