well, are you talking about those leaves that are opening in the water or those that shoot to the top and open like regular lilies? If its the second one, then what i do is just cut them when i first see them (to me they are different because they curl inwards) and that discourages it from sending up shooters.
but if you talking about the underwater leaves getting too tall, i would just say cut the D:
Hopefully, the plant is healthy enough and will make more.