Would i be wrong?

My older sister is always asking my parents for money. She moved out of the house when she was 15 and never went back when she was 21 she had 2 kids.

My parents have paid her phone bill for years, they always buy her kids things that they need like winter clothes. She and her boyfriend both work she together they make over 3k a month. Two years ago my parents bought her a house they paid 10k cash for the house and put another 10k on the house to fix it up. She was supposed to be paying rent to my parents of 600 dollars a month but she wasn't paying so they told her to pay them 400 a month but she still hasn't paid a dime so they are footing the bill.

While my parents were in the process of buying the house I told them my sister has 13 warrants in her name. Because they did a background check and said they found nothing. These warrants were for stealing from her job, identity theft, and unpaid driving tickets. My parents got so mad at me and I told myself that I would never tell them anything else because it wasn't right for them to be mad at me they should be mad at her for not telling them.

Recently my sister told me she wants to turn the house my parents bought into a trap house and even more recently she said she would take an insurance policy out on the house and in 3 months burn it down so she can get the money.

It makes me really mad because my sister is so unappreciative of the help she gets. While on the other hand I do everything right go to college graduate, get married, buy my own house. But when I asked my parents for 3k to pay for my last semester of school they said no.

I really feel like going off on my parents and telling them about my sisters plans and that she goes and spends all her money up on new clothes for her and her boyfriend and fancy restaurants while they foot the bill for her rent and lights and gas she is supposed to pay. She always lies to them saying she didn't get paid enough to pay her rent or she don't have food or clothes for her kids when in reality she is on Facebook with new weaves, new clothes, going out to eat every weekend spending all her money.

Would I be wrong to tell them what she does?