First, you have to understand that a big part of the settlement was Staples shares. Maureen Sullivan Stemberg apparently sold half of these before the company went public... which was a big mistake, because the share value soared. Per TMZ:
According to an article in the Boston Globe in 2005, Maureen received nearly 500,000 shares of Staples stock in the divorce ... but sold half her shares before the company went public.
So her argument might be that Romney was testifying about the value or potential value of the stocks and gave a low valuation which caused her to sell and thus deprived her of millions.... and so pay me.
But if Romney was trying to help his friend, he would have offered a high valuation of the stock, because then Stemberg can give her less. He wouldn't claim the stocks are worth less than he knows they are -- that would just mean Stemberg has to give her more stock to make the same payoff.
This just seems to be a very bad (as it turns out) decision by the Former Mrs. Stemberg.
And, besides, Romney wasn't acting as her financial adviser, even if he did guestimate the value of the stocks. He would have been providing a valuation for the trier of fact (the jury or judge), not for Mrs. Stemberg to take as some kind of financial advice for her to act upon.
If that's the avenue of the complaint: It's not juicy and it doesn't even make any sense. "Lowballing" the value of the stocks just means that Stemberg has to give her more of it, which I'm pretty sure is not the outcome he sought.
