Oh no. Poor guy. It sounds like the hair follicles are in permanent resting phase after the shave. The only thing you can really try here would be Melatonin. It can take up to 3 months however, to see any growth after starting this supplement. Talk to your vet about proper dosing for Lily since we legally cannot tell you that information here, but it is worth a shot.
I would also bathe LIly regularly and brush the area with a soft brush often to hopefully stimulate the hair follicles to regrow.
I hope that Lily gets her beautiful coat back. Best of luck moving forward. Take care! : )