Many issues with her have arisen.
First, there is a rumor that Omar is not her or her father's real name. They used this name to get into the U.S. illegally.
Second, in the U.S. it is easier for an immigrant to enter the U.S. if you are married to a citizen. So they are saying she married her brother so he could stay in the U.S. as he did not come here when she did.
There are other things that are also being looked into.
It seems very complicated and what is being reported is not very clear yet. There are multiple investigations going on. The state of Minnesota, as well as the Feds, are looking into her and her campaign.