How to send a message to a sick ex-girlfriend? If I still love her, . .

Just greet her gently. "It doesn't matter if you are sick. Take care of yourself. I am worried about you. " As you said, you still love her very much. You can visit her directly, be caring and attentive to her, let her feel your warmth, and maybe she will come back to you. I wish your beloved a speedy recovery.