Also, it should probably be noted that professional Vtubers have to be a little more careful about how things affect their image.  They have to decide whether or not they want their viewers think that they have a chance with them.  Being a lesbian gets yuri points but also ruins the fantasy for many male viewers.  Also, there is almost always a certain amount of disapproval when a popular figure admits to not being straight.
Sara may have been aware of her sexuality but wasn't ready to make it public yet