The only real advice i can give you is to do what your trainer says, he/she knows best.
Superhuman flexibility is not nessesary, but it is always a good thing to be able to stretch your leg abit higher. Im always stretching at home when i don't have anything to do, and the result of doing so for the last 8 months or so, is that im Very close to split, and im completely down in the one with leg forth and back. (don't know the english name)
__________________
-+-+-+-+-+-+-+-+
Subform - Allover the place
|