I'm working and have to run to the grocery store to get her some lettuce. In the meantime, can she chomp on the leaf of a lemon plucked from a lemon tree? Not saying she will, but, is it toxic/safe. Might be too tough. I'd chop it into bit. She's 2 years old next month. Healthy but unhappy with her current house (working on it)!
I'm glad that everything worked out, but for future reference, I wouldn't recommend feeding citrus fruits or leaves. Fairly acidic, and, in the leaf's case, hard to digest.
She can wait until you come back from the grocery store with lettuce. I agree with Jeremiah. The citrus leaves are hard to digest and lemons are too acidic.