I'm sorry but I re-read those chapters and there's absolutely no indication that the prince knows that Estien is Estella. In ch 1 Estella says she crossed path with "someone she shouldn't have had to" and the blurred image seems of the prince, but it doesn't say why or how or anything that happened for that matter. Just that he was scary. - no indication that he thought she was a she. Ch 7 he's out to convince a guy to pretend he's a girl and engaged to him to boot... yeah his reactions and his whole behavior is fishy as hell, but not indicating in any way he knows or even suspect he's Estella. The fact that there is an Estella and an Estien is a matter of public record as Estella finds out that her father recorded both names at birth, the prince likely knew from there. If that is what passes as "clues" that Leo knows he's actually her, that's just poor writing.
Well, their "fatefull meeting" was the one in the forest, so the drunk meeting can't be a foreshadowing to that. It would have been, if the prince recognized estien and spoke of that. But he didn't. So the meeting in ch1 is a foreshadowing to something else in future chapters. My guess- it will be reveaked kater, that drunk estella /estien did or said something, that influenced the prince. And in ch7, the questions the prince asks and his reaction to estellas answers... Well,, he already did a very thorough background check on him. Probably put two and two together and then confirmed his guesses. This is all speculation, but often things are hinted or foreshadowed only slightly. So that either a very attentive reader will notice or when reading a story for the second time, or third, or so on.
Thx for coming to my ted talk? *)
" that drunk estella /estien did or said something, that influenced the prince." I can see that being something, but both this and the behaviour in answering are not indicative that he knows he's a she. As you yourself mentioned " often things are hinted or foreshadowed only slightly" and this is done with clear hints, not just open ended imagination and wishful thinking on the side of the reader. The weird behaviour on the sandoffish answers in no way indicate that he thinks he's a she... just that he's put off by the man he hired to be his fiancee, being colder to him than to the guard he assigned to her. that's all

Does Leo know she's a female?