How can a sibling of a U.S. citizen apply for AOS through EB-5 while visiting on a tourist visa?

She may concurrently file the I-526 and I-485 and will be able to legally remain here. Do you have a project in mind for her to invest in?

Your sister cannot stay in the U.S. beyond her several months of authorized stay as a B-2 visitor.

Provided she did not enter with an intent to file an adjustment, it may be possible to donate the necessary investment amount and then file a concurrent EB-5 petition together with an adjustment of status application.

Check the Department of State monthly bulletin to see if an EB-5 immigrant visa is available to persons of her nationality. If a visa is available, file the form I-526 concurrently with form I-485 and all supporting evidence. Certain immigrant visas are set aside for use for specific purposes and a visa might be available after investing in such a set aside project. Because so much money is at risk of loss, I strongly suggest that you engage a reputable EB-5 immigration attorney to guide you to a broker who can provide you with options and to assist in performing your due diligence prior to making your investment.