They love that shit! A woman loves to be treated like a queen. But tread carefully, she may start to expect this type of pampering all the time. But fuck it, if she deserves it give it to her!
OK i have experience on this. i went for a supreme type day at the spa, it was ALLLLL day...and in my opinion it was WAAAY too long. I mean i enjoyed ALL the services, except i felt like i wasted an entire saturday.
Therefore, I think a half day is the best way to go. The services women usually enjoy the most are facial, massage, pedicure, manicure, maybe hair but she may prefer her own stylist (like i do)