Other than the GF, Dolphin and SSR, the spa services are very limited at the other resorts.
If she wants an expanded service, definately use SSR; it is my favorite out of the three and the Turf Club is wonderful afterwards for a nice lunch on the terrace. A little walk over to DTD for some shopping is also nice as well.
The DTD buses go from resort to resort; it is located behind the Rainforest Cafe. She could also take a parks bus back from SSR and then transfer back to her resort.