I wouldn't be at all surprised if this were the case.

snow whites dad wants to protect her daughter from the Queen if he knew she was bullying her so she probably would kill him

^ That is what happened in the book! I ADORE that book and I find it to be a realistic backstory for The Evil Queen. Unlike with something like Maleficent, it makes itself a believable villain backstory explaining why she is the way she is, fits in with the continuity, doesn't make any of the good guys look bad just to make the bad guy look good, and isn't afraid to kill off the villain. I LOVE that book SO MUCH because it's SO WELL DONE that I can't help but believe it to be true. So I'm going with this and no one is going to change my mind otherwise.

mostly, since she wanted to murder Snow White too

I guess since Snow White and Cinderella have similar situations stepfamily-wise, that since Cinderella's father died peacefully that Snow White's did too. That's how I always thought of it.