This page says a bit about displaced persons after WWII.
As to being merried to a person with German name, yes, it was normal, since Germans lived in Ukraine and Russia for centuries. However, it became a great disadvantage politically, when Gemany went with war on USSR. As I mentioned before, people of German origin, Lithuanians, Latvians, Estonians, Bulgars, Tatars, Gypsy, Chechens, and also Ukrainians, and Pols of USSR became a subject to political prosecution due simply to their nationality. About 20 millions did not survive the Gulag ( Soviet concentration camps).
Your grandmother, probably, eventually ended up abroad, possibly, USA (if this is where you are from), since she probably knew where the adoptive family was from. It would be logical that when time came to immigrate, she'd choose USA, just to stay somehow closer to the child she'd given up. Such is mother's heart. Of course, she could also stay in Germany.
Thus, Ukrainian sources can help find out her maiden name, place of her birth, info on her first husband and her older kids. May be she had siblings.