Quality Over Quantity
"Start creating the spells that are apt for you by yourself."
Alephee said before taking a long breath. These were the things that she always wanted to say to Eren. Nevertheless, she recognized that telling these things to Eren, a headstrong individual on his rudimentary path, and showing him what she wanted from him were two different things.
That was not to say Alephee was not pleased with Eren's progress so far. She had seen the guy put in more effort than any other ranker of his generation.
However, more effort doesn't necessarily mean more success. To produce stellar results, the efforts needed to be directed in the right direction.
One had to say the timing at which Alephee had decided to show these things to Eren couldn't have been more perfect. That's because Eren had already seen the effects of the spell he created for himself.