The seats are all pretty decent for viewing in my experience. From an experience standpoint, and if it's a hot sunny day, I'd recommend staying off the Worcester Wall. It's often inhabited by drunken college students and gets brutally hot with no shade.
Sections 1-16 (infield, under the upper deck so you get good shade) are obviously great seats, but more expensive ($30-45). Easy access to concessions and bathrooms
The berm and general admission area by the berm are actually pretty nice too. No shade, but sitting in the cool grass with a drink, watching a game is pretty sweet.
The Hanover deck and bullpen terraces are nice, but depending on where you end up, it might be hard to actually see the game for her as the fencing and the people standing against it can obscure the view for tables that are further back from the edge.