She’s pretty, she just gets overshadowed by her even prettier brother.
This is probably a chicken or egg question, but unless a woman has really low self-esteem I think the only problem with dating someone ‘out of her league’ (i.e. more ‘conventionally’ attractive) is that it’s likely to be remarked upon by friends and strangers. Happens with celebrities all the time, usually coupled with the rumor that the male half is gay.
I do think though that there are plenty of women who like the thrill of the chase and having a guy come around.