Young cats have no fear and can be a handful!
Mine are all senior citizens and still drive me nuts! I think Buddy is 12 (I keep forgetting, my memory is awful) and he climbs on top of the fridge and kitchen cabinets and jumps down. I wouldn't worry about Abby hurting herself. I know she's probably driving you nuts tho. lol.

It must have been nice to see you were down a couple of pounds
Are you still eating the Lean Cuisines?
Can't believe you only had one cup of coffee? lol.

I'm sorry you aren't getting any sleep. I know that is a constant struggle