Federal Tax Filing question - your experience (Dallas)

My sibling is a German citizen and received her green card over a year ago. She is not working but derived income from overseas assets/savings and rental property. Has recently sold her personal residence in Germany and bought a house in the US. She is not tax savvy. I Don't either when it comes to two countries taxes since I've always done it only the US only income.

I understand that she is now a "US taxable resident" from the IRS standpoint. From YOUR experience in this matter (if you have similar situation and been through this for the past few years), can you share your tax reporting experience in GENERAL terms. For example, interest gained from bank in Europe, Germany tax reporting requirements (reciprocality of reporting), rental income for an apartment in Europe, etc? If too personal pls reply vai email to cmdrdata at ya hoo dot com. Thanks.