While she is "under 24" (age 23 or less on December 31 of the tax year) then the test to be a dependent is "does not provide more than half of own support". It doesn't matter if the parents pay more than half or if the more than half is provided by a combination of scholarships, parents, and other relatives. Just that the student provides less than half of own support.
However, when she is over 23 (age 24 or older as of December 31) the rules change. She is not eligible to be a "qualifying child" dependent. The other set of rules, called "qualifying relative" say that she can't be a dependent if she earns more than $4050, regardless of who provides the rest of her support.
So there is a 2 year period where she probably can't be your tax dependent but is still allowed to be covered under your insurance. If your employer recognizes this situation, they should impute you with income for the money they provide for her insurance. It would be treated as if you received a salary that was then used to pay her premium after tax. This is because pre-tax or untaxed insurance premiums are only allowed for self, spouse, and tax dependents.
You could ask the employer about this, or keep quite and wait and see what happens. But it is a thing that should happen, if the employer is aware of her age and keeping track of the rules.
