The way she speaks (not the tone, but the accent) and her cultural ways may imply that she came from Russia
In the episode "French Fried", Todd revealed the fact that no one has ever eaten Mrs. Mush's food. However, In the episode "Daring Love", when Dana told everyone about Todd's new girlfriend, There were several kids eating Mrs. Mush's food.
She had a grandmother that meet a man who loved rules (only to be proven wrong, when Dana read the form wrong), even though she looked like someone from the 1940's
Her only pet friend is Sammy the dead rat, which Sammy may have died after eating the Mushroom Surprise.
Miss Mush is known for making foods that affected three people (Two people, and one pet)
Todd was affected by the Mushroom Surprise which hypnotically caused Todd to fall in love with Mrs. Jewls, only to fall out of love with Mrs. Jewls after eating a "bologna suprise" and vomiting.
Miss Mush is a typo on Google.com.
Mr. Kidswatter burped fire after eating it, saying it's "a little spicy".
Fluffy seems to enjoy the Mushroom Surprise when he eats it.
Miss Mush is so friendly and sweet, even though she is a horrible cook.