Maybe you should try to tell her later,

saying that you feel it's too early to talk about salary thing at this point of time. You would like to focus more on the job responsibility at this moment.

I feel like these days over 90% of the agents ask your current salary and expected salary in the first call.

If you really really cannot move forward with the agent without telling her the salary information, maybe try to give her a range and emphasize your are very flexible with the expected salary (if she asked).

My 2 cents.