Neither Diana nor Veenyle Cr are topend characters. Basically, all your opponent needed to do was play either Pegh or Jean 2nd to nullify you countering with Diana, and then play Troompah to counter Diana. Because you had pill disadvantage after the 1st round, which meant there was no situation you could beat Troompah with Diana, mathematically you lost the match after the 1st round. You are also dead if you go below 9 pills: at 8 pills, Troompah would beat Diana on pill parity.
So your best opening play would have been to lead with Veenyle 0 pills (this means that you will assuredly have a win against Pegh unless your opponent wastes 2 pills on Pegh), then counter with Tremorh or Qubik 0 pills against Jean or Pegh. Either you won round 2 or now you have at least 1 pill advantage. Now if your opponent reads round 3 incorrectly you win the match.