Xena is a tough little pup; she wants everyone to realize she might be small, but she is mighty (at least in her own mind). If she was living in the wild, she would be the Alpha male's partner and would rule the pack in his absence. Xena doesn't really care to be groomed and makes no bones about letting you know it when grooming time comes around each week. If you are not careful, she might even become a little on the aggressive side. Rather than letting her get away with this behavior or sedating her, with a little hard work you can teach her to enjoy being groomed.
While Xena might have a dominant personality, bad behavior is not something you can let her get away with. There are many reasons why she might not like being groomed, including having had a bad previous experience at the groomers. Take your time, work with her, and in time, she will come to enjoy the experience.
While Xena might have been the Alpha female in her pack, she must learn her place in your pack. Take time to show your dominant little dog that you're the protector and provider so she can relax. When it comes time for grooming, take your time, working with her until she learns to chill and just enjoy the process.