Thank you both for the replies. Unfortunately the NBI website is telling her that ID can't be found. Doing some Googling, it looks like this happens with some numbers, preventing you from renewing online.
She has a brother in Manila, so our plan is to sign up for an account on the NBI clearance website (done) and apply for an application, selecting renewal and passport as the document. When we are further in the process (we just mailed in the K-1 package yesterday), she'll set up an appointment online, and send her brother her expired NBI clearance, a copy of her passport, a 2x2 photograph, and a Letter of Authorization, for him to go and claim it, and then mail it to her.
Would this work?