@dotawolfbrother if I had to guess I'd say it has to do with Chion's feelings for Gen and that dude from chapter 12. Especially if you tie in the "it would be a problem if I feel in love with you" line I think it's likely that Chion knows marrying chapter 12 guy and having him take over the temple is what she is expected to do and, while she likes Gen, it is better if she keeps those feelings at bay for the sake of the temple.
@MacMeaties I didn't expect that, I'm gonna hate grandma if she really meant that
I thought she said it perhaps because Chion's reason to stay at the temple was because of her memories in this place, not because she loved it or want to genuinely take care of it
it's like she's fooling her self to live a life she has no interest in
@DepthSailor I think it's more oriented with what you say, she doesn't want Chion to feel pressure to be there and lose her youth because she's chained by her and the memories of grandpa.
@MacMeaties doubt it, ch. 3 already shown grandma onboard with Gen taking the temple by marrying Chion and she kind of gives the stink eye each time that teacher appears.