I wonder if there is another way to say 'get well soon'? Can I say " get over your illness soon"?
OMG! I would NEVER use a greeting that contained the term 'get over your sickness' in it!.... (you might as well tell them to "get over themselves" or, tell them to "snap out of it".... they both sound tactless, harsh and uncaring too!).
How about; "I hope you have a swift recovery & start feeling like your 'old self' (or- even better) very soon"... :)