I'm worried about my sister.

My (I'm a 21 year old Male) sister is 23, she's a lovely girl and autistic, she has never had a boyfriend, a relationship ,a kiss, sex or anything like that, recently she has been encouraged by friends to go on hinge, and has been speaking to a boy, the boy is 21, (my age) and is telling her that she could come to his house, they should go out etc etc, they have been speaking for a week and she seems really eager to say yes, any time I try to tell her to be sensible, take it slow and get to know Him before committing to anything like that, she goes defensive, she's never spoken to him in person, it's only been texts so far.

she's a genius, 4 A*s in her A levels, incredible track record academically, but lacks in common sense and street smarts in the kindest way possible, she seems to find herself in bad situations and panicks when she ends up there. how do I go about talking to her about it? to tell her that I'm happy for her, but also to just breathe, take a minute and make sure that he is worth anything close to her? (I admit, I'm being a protective brother, but I always have been, I worry about her and want nothing but the best for her)