Meryl Streep attended graduation of her daughter Louisa Gummer at Vassar College on May 26, 2013. As Louisa’s name was announced, her mother rushed onto stage to hand her degree
Video with full event (Louisa and Meryl appear at 2:15:25).
I also put the part on Youtube:
Photos (Sorry for the quality; collected from Twitter and Tumblr):
May 25, 2013:
May 26, 2013 – Commencement: