How do you find big momma in mgs4

To find Big Mama in Metal Gear Solid 4: Guns of the Patriots, you must find a Resistance member in Eastern Europe in Act 3. You must then follow him until he leads you to the hide out, which is located at the northernmost edge of the map. However, one cannot simply head to the hide out even if they have played the game before, as the cutscene featuring Big Mama will not be triggered unless the Resistance member has made it there.