I gotta admit, this one gave me a chuckle when I saw it.

It brought back memories of the last picture you made of Ada grabbing Pterano’s beak
Ada grabbing Pterano’s beak (though obviously the emotional atmosphere is completely different

). I assume this represents the nagging you mentioned before.

Speaking of beaks, I noticed that Ada’s looks a bit larger than usual here (though it is EXTREMELY well drawn). The same seems to be true of her eyes, especially compared with tthe previous image (again, however, they look very good). Pterano’s beak and expression are very well done (the only thing I’d change about his head is the last bit of his crest, which is a little rounded on the underside and not pointed enough), and the corners of both characters’ mouths match up quite well with the corners of their beaks.
I can’t help but think, though, that seeing as Ada would have to have her wrist twisted around in order to have her thumb behind Pterano’s beak from this perspective, she’s not holding his head at a particularly good angle to force him to make eye contact with her. Also, the way the line of Pterano’s left wing membrane continues on through his hand to form the crease between his thumb and other fingers makes the hand look very strange. I’d suggest redrawing the thumb (it’s too short, anyway, in my opinion). And again Pterano’s wings seem to be meeting to form a “cape” behind his back and legs instead of attaching separately to his sides.
Both Ada and Pterano’s left feet look very good. Ada’s right one, however, is sort of strange-looking. For instance, it looks like her heel is on the inside of her ankle. Plus, the curve delineating the back of her heel should end at the same level as where the front of her leg meets the top of her foot. I’d also suggest putting a small, slightly curved sliver of visible background above the aforementioned foot/leg meeting point, to show that her wing membrane is not connected to her ankle. As for Pterano, there’s nothing really wrong with his right foot, but his leg seems to attach lower to his body and meld into his side. (Actually, Ada has the same problem of the top of her right thigh forming a continuous line with her side.)
As far as the size difference goes, I think it’s a good idea to keep Ada a little smaller than Pterano, but I think what you have here is pretty good. (I can’t remember how Pterano compares to Petrie’s mother in terms of size, but perhaps you could use that as a reference. Somehow, though, I think of Ada as being slightly larger than Petrie’s mother.) If you’ll excuse a scientific digression for the sake of a fun fact,

real-life female
Pteranodon (or, at least, the fossils which are assumed to represent females) were about a third smaller than the males (a 13-foot wingspan compared to 20–23 feet for the males), in addition to having much smaller crests and lacking the mild overbite seen in males.