It isnt translated, but I can guess Gallade has a pretty decent payroll.

Actually, from my perspective, the Battle Subway staff went out for lunch one day, and Mienshao covered the tab. When Gallade recounted the story to Sana, she thought it was because Gallade ate a lot or something, and packed more for him the following day.

I think it's more of a jealousy thing. If Gallade always had his lunch, he won't be eating/hanging out with his buddies...aka Mienshao...

Look at the face of our Gardevoir.
She is jealous. It's just that. ^^

Jealous Sana is cute

As I see it, it's basically that he's her man, and no other woman is gonna come here and feed him. Yeah, Gardevoir is adorable when she's jealous.

Sana refuse to be outdone some other female.