c995-Killed Harald "The Greenlander" King of Norway. [Ancestral Roots]
According to Ancestral Roots, Sigrid is not the daughter of the King of Poland. That was Gunnhild von Polen, who survived Erik and married Sven Forkbeard, following in Sigrid's footsteps, but Sigrid "divorced" (Viking style) Erik.
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Erik the Victorious was married several times. One of his wives is said to have been Sigrid Storrada ("great ruler'), the daughter of Skoglar Toste, a famous Viking from Vastergotland. According to Snorri, she was mother of Erik's son Olof.
About 985, according to the ancient tales, Erik fought a great battle against his still-rebellious nephew Stybjorn on the great plains of Fyrisvall, near Uppsala. . . .
Erik found it hard to get along with his wife Sigrid, due to her imperious temperament. After a while they went their separate ways. She retired to her estates in Vastergotland, where we are told that she ruled in great splendor and refused many suitors who were hungry for both her beauty and her lands. Among others, she is said to have refused Harald Granske of Norway and King Vifavald of Russia (a petty king of whom we know nothing further). Sigrid has been called "the Haughty" and she seems to have truly earned this surname. [Royal Families of Medieval Scandinavia, Flanders, & Kiev]
Note: From the above I assume that Sigrid "divorced" Erik a short while after the battle in 985.