Hi N2G Your sentence is a little odd without any further context saying what she showed you. Presumably, though, she showed you something inside the bag. The addition of 'up' is not absolutely necessary, but I'd say it does tell you that she opened the bag more than just a little bit.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Yankeethat she opened the bag more than just a little bitGood explanation! Thanks, Yankee.