We're looking for a hotel in Philly for a girls weekend in January/February. We'd like to be close to shopping, good restaurants, possibly a spa. Any recommendations?

Sofitel has a good location, a sauna and a fitness room.
Rooms are quite, big and bathrooms perfect.
Breakfast are nice, the bar is comfortable and there are a lot of restaurants, shops,...as you are in the Rittenhouse, Walnut, Chestnut neighborough.
At Rittenhouse, try "Rouge" restaurant : perfect service, nice appetizers, perfect fish's entree, a marvelous burger and some exquise desserts(the creme brulee au chocolat
worth the test...).
Erik

The Four Seasons is a getaway all on its own. Terrific basement pool and spa and one of the chain's best lobby lounges. The good restaurants and shopping an easy walk. Try Le Bec Fin for an old school grand time.

I would go for the Rittenhouse Hotel. It has the Adolf Biecker Spa and Salon as well as being right on Rittenhouse Square. The fabulous restaurant Lacroix is right in the hotel. The park is right across the street and all the great shops and restaurants of Walnut Street are right there.

http://www.rittenhousehotel.com/

I second the Rittenhouse Hotel recommendation. For dinner try "Tangerine" or "Buddakan" or one of the many Stephen Starr restaurants.

http://starr-restaurant.com/

Another vote for the Sofitel ... great hotel & location ....