Vested Participant does not think they are eligible - Multiemployer pension plan

Recently we have run into a participant who does not believe she is eligible for benefits from the pension fund. After our review, we believe she is vested. However, we are in receipt of a letter from the participant stating she will not fill out any paperwork and does not believe she is eligible for a pension. Under the terms of the plan, participants are required to make an application for benefits. Additionally, the participant has requested that the pension fund office cease sending her letters and calling her regarding her application (or lack thereof). 

My initial thoughts are that if the participant does not want to make an application, there is no requirement that the NEED to apply. 

What is this participant’s age?

Has she reached normal retirement age (under the plan’s provisions)?

Has she reached the plan’s required beginning date?

If she reached normal retirement age, does the plan require an affirmative election if one prefers to delay the pension? Or does the plan treat the absence of a claim as an election to delay?

This is not advice to anyone.

The plan can simply commence her benefit payments in the normal form if she is beyond NRD - they could do this by mailing her a check that she won't cash.  If they delay until RMD, there should be an actuarial increase, or a retro payment to make up for the time from NRD to RMD.  So, she could get a big check at RMD.  There would be a tax penalty on the participant for not receiving RMDs.  If it turns out she is vested, she could face a large tax bill for not receiving RMDs.    

Problem is, she is not permitted to waive her benefit.  She doesn't think she is vested, but the fund office does so DOL/IRS require them to find her and pay the distribution.  She can try to prove to them that she isn't vested, or she can  just accept the money.  The fund may start sending her checks, but it is up to her to cash them.  Fund is required to pay, she isn't required to accept until RMD.  At that point, the tax man could become a problem for her.  

Why does she think she isn't vested?