Well, just being straightforward, the details are kind of murky, since Mae said she was tested for STDs in Canada. But she didn’t mention if she was given a full rape kit, that would search for semen to test for DNA. With only pre-ejaculate, time is a huge factor, because there’s less material to search for.
Being an American, I don’t know the full rights/laws of citizens there. However, I would believe that if you submit for only STD testing, and not a rape kit, they could only provide for certain testing at your will. I wonder, though, if the law changes if you disclose that you’ve been raped, or if there’s more pressure to submit to a rape kit, because a crime has been committed. But, like I said, time is a huge factor, and getting semen from pre ejaculate is difficult. She would have a stronger case if she took a towel or some clothes or something that he came on, or wiped with to corroborate her end of the story.