Insterburg

Hi List,
Hoping someone can be of help to me.
I have a Ernestine Wilhelmina Manthey born abt 1826
at Interbrush, Brandenburg. I have not identified this
place and I believe this is a anglised corruption of a
German word, is it possible that the correct place is
Insterburg.
She married a August Leschke and had a child born at
Grossdorf, Posen.
Any assistance provided is much appreciated.
Kind regards
Wayne