I'm not a lawyer so all I can do s share how I would see it.
If you 'renewed' it's likely that your contract would be deemed to be on the same terms that you signed in the first place. So step 1 is to read the contract your DH signed and see if it gives a termination clause.
If it does, just enact the clause.
If it says the contract is for a fixed term, you may not have means to terminate early. However, as you haven't been sent a new contract you'll need to look at the exchange of correspondence through which the contract may have been renewed. If it is scant, then you could write to them to say that as you haven't received a new contract you're assuming that they are no longer representing your DD. although you may be on tricky ground if, in the interim, you have behaved as though they are.
But - almost any contract can be varied by negotiation and mutual agreement. So even if it looks as though you are locked in, you could just say to them, with great candour, that the arrangement isn't working out and maybe you should part amicably.
Or you can bide your time and look for another agent who you believe can represent your DD better and be easier to get along with, then work out what to do next when she is accepted onto their books. Obviously you won't want two exclusive agents simultaneously, but you don't need to terminate agent one until you have a Plan B. Meanwhile you could work on pointing out the times when the agent is rude to you, which might just help them to behave a bit better and remove the need to change altogether
Hope this helps - if not, feel free to ignore me.
Deb x