18 months in the life of a budgie is a long time. I truly hope that Charlie settles down. Whether he will forget Lacey is immaterial. I don't know if he will. I know you won't and that is the main thing. Sending all my good vibes your way and truly sorry for your loss.
I am so, so sorry to be reading through this, Shirls. Poor dear, sweet little Lacey, poor you, and poor Charlie. Only time can relieve the sadness, but know that all my thoughts are with you and your crew. *hugs*
Rest in Peace, beautiful girl.
We are not Vets, Avian or otherwise. If you have any serious doubts about your budgies' health an appointment with an Avian vet should always be your first point of call.
I read the first sentence and grabbed a tissue before I read the rest if the comments. Tears are streaming now. So sorry for your loss Shirls. Lacey was a lovely little girl. Thinking of you and charlie xx