At this point, I would think about dropping a little note under her door, apologising about the noise, explaining that the cats are young and new to the joy of hardwood floors, but you're sure they'll settle down, and you've bought new rugs, hope it helps. Sorry, sorry, sorry etc. It might help your neighbour realise that the cats aren't causing trouble intentionally.

Hopefully she'll learn to tolerate a bit of a ruckus during the day and early evening, and Boo and Bettie learn to sleep during the night The cats will probably settle a bit as they mature and as cooler weather sets in. Good luck