The final scene of Portrait of a Lady on Fire might well involve one of the most powerful final shots in a film I have seen for a long while; it's still lingering in the back of my brain.

There is no doubt in my mind that Héloïse knew Marianne was there. You cannot have that kind of intimate relationship with someone, that deep of a connection, and not know when they're staring straight at you, even from across a room. The way they kiss eachother, the way they observe eachother, their whole essence woven together.
Take the tragic story of Eurydice and Orpheus they read together earlier on.
Héloïse however didn't turn around, deciding to choose the memory of Marianne instead. You can tell just through her breathing that it is taking all her strength not to just look round, to even steal a glance at her forbidden lover.

It's heartbrakingly beautiful.