Which spa are you visiting? Where are you staying?
The spa at the Whiteface Lodge is pretty impressive (alas expensive). Its a mere 6000 square feet and has just about everything you can imagine. You might be going to the spa at Mirror Lake which is supposed to be excellent as well.
For eating I suggest for something special: The Whiteface Lodge (thats the place we own in), The Lake Placid Lodge (ultra special, alas pricy), the Cottage on Mirror Lake (part of the Mirror Lake Inn complex)) for lunch (its a tradition for a lot of people!) - best views in town on the water with views of the high peaks, or the Moose Lodge direct on Lake Placid (if its open) - best views of Lake Placid and Whiteface.
For a special night, visit Maggies Pub in the Lake Placid lodge, or Kanu Lounge at the Whiteface Lodge.
Shopping is all on the main drag so hard to miss anything. Stop in at Ruthies Run. The ADK store to pick up something for your daughter.
If you like all things ADK stop in at the Ray Brook Frog in Ray Brook on the way in (assuming you are arriving from the west. There is another such store coming into Lake Placid from the west on the right just down the hill as you pass the Price Chopper along with 2 others on Main street.
For excerise / fresh air do the traditional walk around Mirror Lake... if you get thirsty take a break at the lake Placid Pub and Brewery across from the beach.
Take the gals out for a tour on Lake Placid. This is a great tour. You'll see a lot of great adirondack camps on Lake Placid, find out who owns what, lots of history etc. Views are priceless (including Whiteface of course). See http://www.lakeplacidmarina.com/
Reasonably priced. Been on it a few times taking friends out to see the lake.
Unfortunately none of the major events are on at this time of the year. Always fun to visit the bob sled run or watch them jumping off the high tower in the summer...
Lots of options for hiking! Maybe thats not on a girls spa weekend agenda though lol.
The Whiteface Lodge: http://www.thewhitefacelodge.com
The Lake Placid Lodge: http://thelakeplacidlodge.com
Lake Placid Marina (Boat Tours): http://www.lakeplacidmarina.com
Moose Lodge: http://www.whitefaceclubresort.com/club/moose_lodge.php
The Cottage (on Mirror Lake): http://www.mirrorlakeinn.com/dining-cottage.cfm
Ray Brook Frog: http://www.raybrookfrog.com/
Ruthies Run: http://www.ruthiesrun.com/