I've seen her a number of times, and am responsible for her one review here on UKP.
She is quite pricey, particularly if you want both sex and dom, but she is very good. Her "chambers" for dom meets are well kitted out and are in an industrial area on the west side of Cheltenham, and are fairly discreet.
If you can afford her then she is worth a visit. She does allow oral and rimming, and can give dom as mild or severe as you want it.
Another excellent option at more reasonable prices is Morgan -
External Link/Members OnlyI have reviewed Morgan also and she does allow (and enjoy) receiving oral and rimming, plus is good at domination at any level. Her premises aren't as well equipped or "upmarket" as Zara, but she is good fun. Don't be put off by Morgan's lack of AW activity or feedback - she is very well established and just doesn't bother with AW very much.