If you're talking about the time Katniss found him camouflaged in the arena in the 74th HG (which I think あなた are) it's because she feels she owes him for the burnt パン years 前 and because she thinks it's her fault for not running away from Cato and making Peeta fight him, causing him to bleed. Just one little thing, she doesn't 愛 Gale at that time. Oh, and if this wasn't the answer あなた were looking for, I apologise.
