If the girl is adult (as you mentioned, she is 27 years of age), she cannot be forcibly detained even by her parents. Likewise, she cannot be forced by her parents to marry a particular individual against her will. She can approach the courts in this regard by filing a writ petition; she can do so through some friend etc. acting on her behalf.
The girl, if she is major, can have a live-in relationship with an adult boy, as held by the Supreme Court. It is permissible under law.
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