Some space marines like to make their own power swords or other equipment. Seriously, these guys spend a lot of time learning how to kill things. If they are also tech-artisans, how hard can being a tech-artisan be? I know there will be a lot of disagreement over this last statement ("but they live hundreds of years!" "they don't spend ALL their time killing!" etc., etc.), but I don't see many people trying to learn HOW the universe functions, just how pieces of it function independently from the big picture.
Space Marines also have their "human" personalities erased and huge amounts of combat indoctrination downloaded directly into their brains, so they're not so much learning as having their minds imprinted with someone who once understood how to do something. Also the Adeptus Mechanicus actually does consider anyone other than them trying to understand how something works is a heresy, and I don't think routine experimentation is going to protect your crew from their wrath.
It's not that we can't afford to get more teleportaria but rather something for her character to do. Her previous pass time of getting live Xenos and studying them has been severely curtailed what with us having Death Watch Marine onboard now.
See this is why I have teleportariums be extremely rare to prevent a Rogue Trader from approaching it with the air of "Boy, we really should go down to Costco and order up another dozen or so."
Also clearly the Death Watch Marine should become her next subject for experimentation. If she likes tinkering with things, why not arrange for certain components to "malfunction" as the Space Marine is walking by and measure his reaction time. Turn the entire ship into an elaborate maze that contains not-quite-lethal death traps, and if confronted act surprised that the Space Marine doesn't appreciate her keeping his reaction time sharp.
We're refrained from buying archeotech to keep it feeling special and to keep the flagship unique. And my sister likes your suggestion. Our poor DW player won't know what hit him.