i really don't know what to do..

yesterday, i had a terrible day. I didnt even know if i was going to make it through the freaking day.
Later, my mom came home from work, really depressed.
She said that the guy that came over to check our house that morning ruined ther day and she felt like crap.
She told me she felt like crying about nothing.. then she started crying..
i felt the same way, but i didn't say anything.
Then, she said she was afraid.. i asked her why. She told me that she was scared of how low she felt.. and that she was afraid of getting so low and so depressed that she would commit suicide.
I didn't know what to say.

that scares me. She is so mentally unstable.. my dad told me that he's afraid that one day she's just gonna lose it and kill him.. or us.

what am I supposed to do about this? it's like an adult asking a stupid child(me) what to do..
i don't know! i'm as lost as she is, she just doesn't know it.
And I can't tell her.. She never understands me and my problems.. that is not an option.

but what do i do?
i'm scared.
She also asked me yesterday if I remembered having a bad childhood and if she mistreated me. I told her no.. because i don't reallly think so.. but she wasn't that nice to me, she's never been,
Sometimse i think she's jealous of how well i get along with my dad.. and how much he loves me.
i dont know..
Sometimes i blame her for all my anxiety/depression problems.. they are hereditary. Plus, she makes me so unhappy.. i do love her though.

i feel like giving up. what can i do to make her feel better when i can't even get myself to feel better?

anything...

I feel bad for my dad/brother.. they have to live with two psychos..

this is hopeless.