(or for a more modern look, EnLiven)
Enliven is a verb, giving an energetic feel to the name.
The whole reason for going to a spa is to refresh, renew, and energize-- the definition of enliven.
Having one word keeps it simple, and easy to remember. This also allows for more possibilities with a logo.
A Google search did not find any spa anywhere named Enliven, and the domain names EnlivenSpa.com and EnlivenDaySpa.com are not being used.