If you show proof that you have a trip booked and need one ASAP, you can go to the nearest passport agency office (Detroit maybe?) and you can get one in a few hours....at least that's how it was years ago. It's more expensive.
I got my expired passport reissued in Miami. Couldn't get on the plane that Saturday morning. Had to spent 2 nights in Miami to wait for passport office to open Monday. Got it issued that morning and on the plane that day. Just make sure she has 2 passport pictures to present to them before you go or she'll have to leave to get pictures and then go back and wait in line to get it done. Hope she knows her original number to help look it up or there might be more hoops to jump through. She might need to take her birth certificate with her and some other form of ID too..
Unfortunately it looks like my daughter will NOT be making the trip with us because of her lost passport. She lives in Chicago and could get to the US Passport office tomorrow morning but does not believe that the office will be open or will let her in. In the days of Covid there seems no way to expedite a passport. We're so sad.
We haven't seen our daughter in over a year. She moved to a new apartment May 2020 and we've only seen it on zoom. Somehow in the move she thinks she must have lost her passport and didn't realize it until last week. As of right now it looks like it could be months to get a replacement.
Just another example of all the things effected by the pandemic and the poor state of affairs or government and businesses are in.
Hopefully something else will work out or she'll find the passport, but it might not hurt for her to contact her congressional representative to explain what's going on. I participated in the TripAdvisor discussion linked below when we were trying to get a new passport last year, and several people mentioned that being helpful. In most cases, this was in situations where a passport application was already submitted and just delayed, but there may be something that can be done here. I never would have considered it, and it seems like there are staff members that deal specifically with passport-type issues.