Shipmaster Sane
You have been weighed
I would probably compare and contrast it to the Siege Beetle (CR16, MM5), who's "as wide as a barn and longer still" (Gargantuan) so considerably more massive than the Queen, sprays fluids all over that blind people, has a paralyzing bite, is frighteningly quick for its size, can fly, is resistant to cold and fire, immune to electric and sonic attacks, has damage reduction.I don't see any material difference but whatever it's not that important. Hmm what would you org a queens cr at for 3.5? I'm saying cr19ish maybe?
You could argue, perhaps, the Queen has the DR and charge attack, and has the advantage of Acid blood, but it probably isn't stronger or more durable (if not much less strong, if I'm remembering it's much smaller), and lacks flight, immunities (except presumably to acid), and the special "status" attacks.
Perhaps it's more comparable to the Remorhaz? A "Huge sized" hard shelled monster that destroys weapons that hit it. The Remorhaz is considered "lopsided" in terms of CR at 7, it's extremely difficult to run a Remorhaz encounter that doesn't either instantly kill a player or two, or end with the Remorhaz dead from one spell. It's considered one of the worst monsters, mechanically, in DnD period, top three even. I digress.
Take a Remorhaz, swap out "EX: Heat" with "EX: Acid Blood", Replace "EX: Swallow Whole" with some kind of extra damage effect on a successful grapple to represent the second mouth (Simplest way would be free bite attack damage wise). Give two claw attacks and a tail attack per round in addition to the bite attack, and you're done.
If we say the Xenomorphs are "vermin" and thus remove the Remorhaz' biggest achilles heel, add three attacks, take away swallow whole, take away burrow speed, add a "rend" or "constrict" style "free attack on grapple" ability...
CR 7-9, depending on how you want to calculate CR, very technically (CR7, like the Remz, it gains a lot but loses a lot, they're about the same threat level), or more based on play experience (CR 9 to represent the threat of losing weapons, this would be ignoring the Remz' CR, essentially arguing that it is too low).
So in short, I'd directly base it off the Remorhaz, and give it a technical CR of 7, and a personal CR of 9.