Being a step parent

Brenda • Happy mommy of 3 beautiful girls And expecting my 1st Boy in November 💙
So tonight was my breaking point, I flipped out. My boyfriends 4 year old has been so angry with me because her mom is hardly in her life. She calls me "mommy" and i am her mommy, but tonight it was her bed time and right now we live with my boyfriends mom while our house is getting built.. i ended up losing my cool with her and yelling outta control.. she knows If she crys she gets her grandma's attention .. so while she's crying and freaking out.. i yell "I've had enough, no more! " And she started screaming so grandma came out and grabbed her and said "what did you do to her?" And don't like me forget to add, my boyfriends daughter told me she's gonna kill me 2 nights ago and was kicking and swinging at me tonight .. maybe that's why my temper got outta hand. I'm losing my patients. . Any advice out there? I feel like my boyfriends mom thinks I hurt her and I'd never .. she told me she saw me pulling her hair, if that was the case why you asking what I did to her? I'm so upset and confused. I have a 2 year old of my own and I'd never hurt either of my children .. :(