She became the co-founder of this tech company along with her college classmate.

co-founder 是由前缀 co-（表示“共同、一起”）和名词 founder（创始人）组成的复合名词。co- 表示“共同参与”，founder 指“创立者、创始人”。 co-founder 指“共同创立某个组织或公司的人”，即“联合创始人”。