I think that you may have grounds for appeal.
You are permitted to bring dependents with you, regardless of whether your permit is as an ICT or a new hire. Also, it is permissable to have dependents over the age of 18 if she is totally financially dependent on you. If she has been living with you and has been studying full time, funded by you, and intends to study full time in the UK, then she can come over as your dependent.
Immigration specialists need not be that pricey...I'm not! If you want to PM me, I would be happy to take a look at the refusal and see if it worth appealling.
Vicky