Hi,
My DD has been working with 2 agents for commercial work -- long story, but we signed with a new agency who agreed to let us stay with the old agency for a few months so as not to ruffle too many feathers. The old agent was aware of the new situation but was hoping to be able to coexist with the new agent.
The new agent has asked that we be exclusive but I am dreading having to call the old agent on the phone. (She's a bit dramatic!) Is it totally rude to state our decision in an email?
Thanks for your advice.

I would suggest doing it through email with a return receipt. Maybe even certified mail.

This is a business decision, you are not breaking up with your boyfriend.