I have a feeling you are right. Before you clued me in about fultonhistory.com all I had to go on was what I could find on ancestry.com which was that one single US Census form, and it listed her parents last name as McGrath. So I, wrongfully, assumed that was their last name. But last night after browsing through the syracuse papers on fulton I noticed that all the blurbs on her I found kept saying McGraw. So I am now leaning towards McGraw as the last name and will change that soon. I think the census form taker heard it wrong. Maybe it was a real thick irish accent and he/she heard McGraw as McGrath. I believe the paper clippings from several editions listing it as McGraw outweigh the single census form listing it as McGrath. So I will change that. And I was wrong about her sister as well. I have her sister being Mary, but apparently it was Anna.
Another paper article I found from syracuse has Margaret Tucker getting a letter of appointment for her late father, Patrick McGrath. That is how it's listed in the syracuse paper saying that Margaret received a letter of appointment for his estate. So I am back to be unsure if the last name is McGraw or McGrath again. Sigh.