My sister had graduated that year, and I attended the commencement ceremony. And she had talked about Visigoths and things like that that she had spoken about in her commencement speech. And essentially she was speaking up for the teachers and the biology textbook.
My sister studied biology
The context says that my sister spoke about biology textbooks in her commencement speech, so she definitely studied biology. The system probably found it hard to make the link
( z1 study :ARG0 ( z2 person :ARG0-of ( z3 have-rel-role :ARG1 ( z4 i ) :ARG2 ( z5 sister ) ) ) :ARG1 ( z6 biology ) )