Are you looking for convenience or value or a balance of both? I don't know about any packages other than the day trip option which I wouldn't recommend. There probably is not much to be gained by going with a package that includes springs, hotel AND transportation. The only Tabacon luxury packages that also include transportation start at $1700 plus tax for just 2 nights. They have cheaper 2 nt packages w/o transportation and fewer bells and whistles ranging from just $1000 (d.o.) for a standard room green season to $1900 for their top suite peak season. I don't know what other local hotels offer. I'd imagine they'd have to be much simpler and cheaper but still no huge savings over putting together one's own package. Its easy enough to do this all "a la carte" and it gives you much greater flexibility as to where you stay and what you do.
Hotel door to hotel door transportation can be done either Grayline (
http://www.graylinecostarica.com) or Interbus (
http://www.interbusonline.com) for $29/pp each way or if you're at all adventurous you could take the public bus for just a few dollars each (I know that's the way your girl would do it herself).
Once you're there you can stay at any number of nice hotels. Much has been said about the Tabacon Resort. I have stayed there myself a couple of times. If you stay there you'll save some money on admission to their hot springs. However, you probably won't save as much as you think since they've raised their room rates so god-damned high it more than offsets that advantage unless you plan to spend every minute you can in THEIR springs. Their rooms are very nice but much more expensive than equivalent rooms elsewhere in the area.
If you don't stay there they'll still get you with their ridiculously high spring rates. Those rates are now $35 for just an evening pass (good from 7-10PM), $45 for a day pass (good from 11AM-10PM and various packages inlcuidng meals for even more. You used to be able to save quite a bit with the evening pass, but not true anymore.
The Tabacon hot springs are very nice and I recommend everyone bite the bullet, pay the money (before they raise it even more) and go there at least once to check it out. But you should be aware that there are also other very nice springs in the same area. For example one directly across the street from Tabacon costs only $10/day and even less for your tica novia. It doesn't have the fancy mud-bath or massage treatment spas, but unless you want to spend the extra money for that for your chica do you really care. She'll probably also feel more in place there than the fancy Tabacon across the street though you might not since the visitors there are almost entirely ticos.