Khalida Matsoukis is one of the many supporting characters that shows up in the Sylphverse. She's the second non-family, major character to show up in the stories and easily Sylph's best friend and biggest fan.
Khalida is unusually strong for her size, although not anything like on Sylph's scale (few are). Since meeting Sylph, she's started a more regimented approach to weight training and body sculpting; she wants to be strong in order to help her with her dancing, but she doesn't want to be bulky.
Without going into too many random details, I'll just point out that you can find out pretty much everything you want to know about Khalida in her profile and in the many stories set in the Sylphverse.