What it means
A deponent is the individual who gives evidence by affidavit. They are the person swearing that the contents of the affidavit are true, and they sign it in front of an authorised witness. If the matter goes to a hearing, the deponent may be required to attend and be cross-examined on what they said in their affidavit.
How it's used
As the deponent of the affidavit, Maria could be called to court and questioned about the events she described.