I am curious if there are any resources that make it possible to have someone keep their eye on my disabled sister in law and make sure she doesn't leave the bus and makes it to her destination I know airlines do it...

Yes the first two seats by the driver are for the disable.

Might have to pay extra for disability services in the two front seats of the bus. I believe Greyhound has escort services all you have to do is ask. There was a youngster traveling alone the driver kept tabs on the child

Maybe, they did as little as possible for me... they might make more effort to help her.

I agree with Dennis. I would not put a loved one with disabilities on a bus alone.

Depending on where your at and the destination, the bus driver would be the only one who could monitor her, and some of those are very bad at their job. The only foolproof way I can see is for someone to go with her. A loved one if they're at all vulnerable, will be a target of unscrupulous people, sorry to say. Good luck.

Call the station and ask