Yes, you can freely use lilies as long as you have not completed charging Misery, or you can ignore lilies and overcap if you don't need them for movement or healing. The loss now would be if you had Misery ready but used a lily heal instead; or you did not enter the 2min party burst window with a Misery charge ready. Whether you use your lilies or let them overcap does not matter as long as you avoid those two things.