Like, Rin just made a huge detour and cancel her own camping just to check on Nadeshiko. The first is just that Rin don't wanna have come all the way here for nothing and the second is just that's it's late and same reasoning than before, Sakura is just nice because she know all the road that RIn has done to come here.
This is moving the goalposts, tho. You can certainly ship Rin with Nadeshiko for a variety of reasons.
But there are clear interactions between Rin and Sakura that quite easily lend themselves to shipping if that's how you wanna roll. It's not some huge mystery.