The fact that you're worried about people finding out about your plan to give a Christmas present to your friend, and then getting "the wrong idea", definitely makes me get "the wrong idea".
Isn't gifting someone outside of like family or very close friends on Christmas (aside from kids) typically kinda viewed as a more romance-y thing there? I don't mean exclusively romance-y, just, "stereotypical romance-y vibe" sorta thing? I know it's overplayed AF in most anime/manga, and obviously in this one we have Adachi who is clearly having a difficult time convincing herself that it's NOT weird for friends and it's NOT romantic, etc. But I'm not Japanese so I don't know the real truth of it.
All I know for sure is that it's pretty traditional to have fried chicken for dinner.
Which makes me wanna say that Adachi should just Leeroy Jenkins the whole thing, cuz worst case scenario, at least she'd have chicken. /horribly unfunny doubly nerdy joke