I agree Greg. If they offer a package, but all means take it! But I've never heard of a generous package if you were put on a PIP.
I don't recommend that she put notice in today. Instead, I'd look at the 90-days as my severance and start working full time looking for another job outside the company while doing the minimum on the PIP.
While most people in HR or senior management will suggest that PIPs are meant to improve performance, few will admit that they are there to protect the company from lawsuit, and the number of people retained after a PIP, in my experience, is EXTREMELY low. After 30+ years in the corporate world and management, I have yet to personally see anyone recover from a PIP. Most justifiably so, but there were others that just had bad timing and a poor relationship with their manager (notice I didn't say leader).
Bottom line - If the manager was truly interested in saving his wife, the manager would have coached her before it got to a PIP.
I know people who were put on PIPs only to work their tails off to meet the goals and they ignored looking for work outside. Because PIPs are carefully written to protect the company, they can always be interpreted to be missed. Then, at the end of 90 days of stress and pressure in trying to keep the job, the employee provided enough time for the company to find a replacement and ensure a smooth transition and doesn't have another job outside the company.
Again, I wish her the best in any path she chooses, but my suggestion would be to starting looking outside immediately. Then, give notice without telling them where she's going. If they know she's not going to a competitor, they will milk those final weeks to make sure they get the most out of her. If they think she's going to a competitor, they will likely terminate ASAP and, good companies will pay out the notice period.
Again, to all posters - your insights and opinions have been extremely helpful. The above quoted e-mail best summarizes my wife's situation... especilaly the unmotovated manager who has no interest in "coaching" her. The weekly meetings are basically run arounds where she is constantly thrown a "shiny undefinable object" that she has to try to quantify and chase down. The first 60 days were wasted on these crazy "scavenger hunt" performance plans.
Bottom line - She will be resigning.
Good news is that she has had one interview 3 weeks ago and according to the head hunter, she is a very strong candidate moving forward. She is a very proud and I think from her standpoint would rather stand tall and resign than face the humiliation of being fired. Yes - the company wins in the short term, but she does not have the stigma of being escorted out the door...