Egg-barfing is fine for something that does a parasitic birth. The species does this with the facehugger, the Predalien just happens to be able to do it. That part I think is fine for what it is especially given the egg-morphing being a thing. They have to have some means of creating embryos without a Queen, the Predalien is just an extreme example of this.
Though I do have some reservations on it because it simply hasn't come up before or since. We have no idea if this trait was caused by the Predalien being a hybrid and some wire got crossed when it picked up the Predator DNA (especially not now seeing as we have no idea if Scar was a mutant or not). There was also the issue with it being unclear if it was a Praetorian trait and since we hadn't seen a Praetorian prior that this was simply new information.While the Praetorian had shown up in the EU prior, the movies take precedent here. Then we have the possibility that Chet was a young Queen and she happened to look so different due to her host being Scar. We know some Queens can look different or do weird things with foreign DNA. The Resurrection Queen made a womb after-all, bizarre behavior or appearance is not out of the question for a hybrid.
I don't remember supplementary material addressing this either. Subsequent Predaliens (chronologically and simply being made after Chet) near as I can tell also don't do this, even those that resemble Chet. Ultimately this ends up making it the elephant in the room where it's not unheard of for this to happen, but it just happens and its never addressed why it happens other than BTS information which isn't necessarily canonical. The film doesn't have to explain this, but it is weird that this wasn't touched upon even if it was unique to this specific individual. It's not offensive in of itself, but it's basically awkward that this trait seems to be such a one-off.
