He’s, doing his best , 

Diana Cavendish’s (genuine) smiling post

Times Diana has smiled (genuinely, not the mean/taunting smiles like in the first OVA) at her present age (not as a cute little baby at Chariot’s performances) that DO NOT involve Akko:

Episode 2, while trying to save the Memorial Tree. (That’s two screenshots, but one instance.)

This tiny little accomplished smile she does when dismounting her broom after breaking a speed record in episode 3.

Times Diana has smiled (genuinely) that DO involve Akko:

End of the 2nd OVA, only after she sees that Akko is safe.

End of episode 3, while acknowledging and praising Akko’s passion.

So far, these are the only times Diana has genuinely smiled at her present age.

As you can see, 2 times have been due to her own accomplishments. 2 times have been because of Akko.

Put another way, 50% of Diana Cavendish’s smiles thus far are directly and solely linked to Akko.