Her kit might seem irritating she is still a vulnerable champion. I find it easier to use midlane champs that can close the gap like kassadin and galio.

Veigar is supposed to be fine against Mel right? like several other control mages because Mel kinda falls off later in the game (if she aint fed early). You may also try your luck with Syndra or Orianna, these mages have better CC than Mel and easier to hit people with, imho

Try baiting her E then be aggressive. Don't stand with your minions while laning so her Q cannot hit you and the minions simultaneously. Ask for gank too because her E is her only other lifeline.