I think Morningleaf does not need a stallion, because lets face it if Morningleaf chooses Brackentail or Star the other side will get mad and declare war. Morningleaf is a strong capable mare she was a spy and through the Ice army and the Black army off the location of the hiding steeds in the trap. That takes guts, and how many times has she saved her friends? She even found her way out of the lava tubes! So many reasons why she does not need a stallion and Morningleaf can be friends with Backentail and Star with out choosing one.