Unless the guardian was appointed by the state, the guardian is unlikely to be paid by the state. It is my understanding that DSHS has either eliminated or drastically reduced funding for state-appointed guardians, which leaves a lot of abused kids and disabled adults out in the cold. But I digress ...
It would help to know more about your specific situation, but as a trustee, you are not obligated to sign anything agreeing that fees are reasonable if you do not believe they are. Your fiduciary obligation is to protect the resources of the trust so they can be used for the ward's benefit. How did your daughter wind up with a non-family guardian anyway? Under what circumstances was the guardian located, and what (if any) discussion was had concerning compensation? How involved was the Court? Your situation smells fishy to me.
Guardians and guardians ad litem are entitled to charge a reasonable fee for their services, but the reasonableness of their fees are subject to review and approval by the Court. If you oppose the fees, you should file a response explaining why you do not think they are reasonable.
As for the petition to require an accounting or removal, you may be required to provide information about the funds held in trust and how they have been spent. However, it may depend on the specific terms of the trust instrument and the context of this dispute.
Realizing that the trust is small and runs the risk of being depleted, I strongly encourage you to contact an attorney in this situation. Guardianships can be complex, administering a special needs trust can be difficult, and I sincerely believe that you would benefit from a lengthy consultation with somebody knowledgeable in these areas. In addition, without legal assistance, you may find it difficult to oppose this guardian's request. Please consider it, and understand that time is of the essence.