So I'll try to make this quick.

My sister got married July 16th 2016.

Her entire marriage has always beeen just awful. Even before they were married they were awful to each other

Well recently I got a job at a local gas station and my sister has been coming to my work on and off and hanging out...

But I just found out she's head over heals for one of my coworkers.

Her husband will text me at 4-5 am and ask 'hey do you know where your sister is?'

And the next day my coworker will tell me she was at his house. And that they "don't do anything" because he supposedly has "morals"

My sister will tell me 'hey is brian asks I'm at the ER Oaky (brian is the husband) so he doesn't know why she is at my work.

I feel so bad for him but then again I don't because they beat each other. They're so bad for each other.

What do I do? Tell him?

I keep telling her I don't want to be involved because what she is doing is wrong, but she doesn't care and she still uses me.