How can I get my mom in a better mood?

Okay, so make a long backstory short, my dad is in a detention center for 30 days. I am staying strong (i'm 16), but my mom sometimes is like a 3 year old. I get I don't do much during the day (I babysit and petsit 2-3 out of 5 days), and she is running my dad's business without him and stuff Sometimes she is like "Ashley, I am strong, its only 30 days, and we get to visit him, I'm a-okay (:" and other times she throws LEGIT hissy fits. Like this morning I mowed the lawn, and I said that the grass was piling up on the wheels, so she took a hose and rinsed them off, but she got a little water on the hot motor, so now it won't start (I know if I leave it overnight, it will be fine, its happened with my dad before) and so she was like I F*****G BROKE IT WHY DOES ALL THIS S**T HAPPEN TO ME?!?!?!?!?!?! and then she threw a dining chair at the fireplace. Then she was like GO VACUUM YOUR ROOM LIKE I ASKED YOU TO FOUR DAYS AGO!!! And i apologized and she was like Next time, just listen to me and do what I say!! Then about 20 minutes later, she came in with a "i don't wanna be here, saying this to you" face and said "sorry i freaked out". I know she's stressed, but sometimes I'm like who is the adult here?? we're going out with some friends (mom's friend has a daughter who is my BFF) and I just want to make sure she isn't like I DON'T WANNA GO OUT or be in a pissy mood the whole time.....HELP ME! Why is she acting like a tantrum brat!?