I'm not sure of the details of this plan benefit or this DRO, and I am no actuary, but my first instinct was that it was probably going to be a bunch of work to get her the same dollar amount. I am bad at the DB actuarial stuff, so I have to plead ignorance. But despite my ignorance, I agree with your perspective that this QDRO seems to me like maybe it would not be helpful to her.
But if the plan qualifies the DRO, I think compliance is obligatory for the plan, isn't it? The plan could tell the participant "if we use a QDRO, you get $X overall, and if you withdraw it, you get $Y" and then if X is better or worse than Y she could choose to withdraw the DRO or not. But if it's valid and the plan qualifies it, and for some reason she had decided to proceed, then even if it's worse for her I think the plan still has to do it.
It's possible that the DRO will not be qualified anyway, depending on how it's structured and on the plan procedures.