Having some issues with my boss?

Hi, a few months ago my boss asked me if I would like to become the store manager and I was very excited and said yes. He told me when I started training I'd get a raise and then once I become the manager I'd get another raise. I've been training for 2 months now and I never got a raise nor asked for one. The manager now though always accuses me when anything isn't just so. She accuses me for adjusting her desk chair, messing up her keyboard by pressing num lock and such, and today she said her computer has all these viruses that I got on her computer from me going on Facebook and Yahoo Mail (she also goes online for personal use.) The manager is my boss' sister in law so by me taking over they might have some trust issues. Sometimes she says she doesn't know if she picked the right person because I didn't remember something unrelated to my job that was days ago. It really hurts my feelings what she says because I am very trustworthy and they don't realize how honored I am they asked me to take this job. We are a small independent pharmacy. How much is too much to take from her and for me to say screw it? As it is I didn't get a raise and now any small thing that is out of place I get scolded on I just don 't know what to do.