I love the two Momentus XTs that I have in my laptop, seriously amazing notebook drives.
If the mSATA is configured as a cache in firmware it may be possible to configure it as a standard drive, it should be attached as a storage device just like anything else, nothing special there.
What I would avoid doing if I were you is having both the Momentus XT and the mSATA cache at the same time. The Momentus XT's internal cache means that some data could be cached twice, and that's just asking for trouble.
If you do decide to give the Momentus XT to your wife you won't need anything special, just a 2.5 -> 3.5 drive caddy, costs about 5 bucks.