Turns out Mrs. B's accent isn't as neutral as I thought:
"Native Wisconsinites pronounce some words a little differently than their peers across the country.Read more here.
Milk can sound more like melk.
Bag can sound more like beg.
"Two dramatic linguistic shifts are pushing toward the state from opposite sides. From Minnesota to the west comes the shift known as the Low-Back Merger. In this shift, the "o"sound is merging with the "au" sound. Example:
Caught is sounding more and more like cot.
"From the Southeast comes what linguists call the Northern Cities Shift. Examples:
Cot is sounding more like cat.
The female name Dawn is pronounced more and more like the male name Dan.
The name Dan, in turn, is pronounced more like Don."