It could be both "lean into him" and "let him continue".
That's exactly what I would like to have in the game. Let him continue would be a neutral/friendly option, while lean into him would be more intimate with Tav doing something extra like grabbing his hair or putting their hand on his back, and Astarion getting more comfortable in turn. Tav should also stop wriggling about so much, they look like a dying fish moving their legs like that.
