ETA: I see Brit's post now.
At 5 months old, Lucy is still very much a puppy. You have another 1.5 years of development ahead of you.
Give Liz a safe place to escape Lucy when she wants (something more comfortable than the kitchen table).
Supervise when they are together and give corrections. Work on training Lucy on basic commands and practice in front of Liz or with her. Take them on walks together. Get involved and promote structured and calmer activity as much as possible. Don't wait for Lucy to magically calm down with age. The maturation process also requires training.