Little do I know, since I hardly ever work with people who pose for me (I find posing people incredibly difficult and therefore applaud you on this photo overall!!!), all I could do was try to help you find out why she later said she "looked awkward". She might not have felt how many muscles were involved to keep her on those rocks like that, she may have felt like it was normal to be sitting there (using all those muscles), if sitting there was what she had (also) thought was a good idea. And only later, upon seeing herself, she realised that "hang on! something's wrong here".
Really, I am the wrongest person to be asked for advice, but maybe, when you have a patient, willing model (like you seemed to have had in her), who is happy to go along with your ideas, and is happy to offer ideas of her own, you might start to watch for such tell-tale signs as sticking-up feet (not relaxed), and grabbing fingers?
But hey, best wait for the pros to come along, though they rarely come to this forum. They much rather meet in the professional's forum... a pity.