If it is a genuine question, then people should answer that...
normally, children who grow up in west, have many questions about praying, eating halal chicken, gf/bf, etc...
the main reason is people try to do follow western culture, trend, and their own wishes... Then they came to know that the 'religion' is prohibiting them.. then they raise such question.
If she is really in pursuit of answer, she will find the reason for. If her inner-self is questioning/objecting the marriage institution, then she will be rebellious. Anyway her parents need to educate her.
I can tell you my experience. I was in Italy. I didn't do drink, or have gf, etc.. So i thought, may be it is ok to eat any chicken available in my uni canteen, as it was cheaper and appealing. Though, I didn't but young people find a reason to justify what they need to get.
In summary, there is some hormonal activity, not a philosophical arising, and her fault is, she posted it on twitter. I think one way or another, we all had some contradiction in our minds, when we are young.