Quote
Redson
When Darcy does declare himself to Elizabeth, she can scarce believe her ears: "In vain have I struggled. It will not do. My feelings will not be repressed. You must allow me to tell you how ardently I admire and love you."
Elizabeth's astonishment was beyond expression. She stared, coloured, doubted, and was silent.
Did she doubt because Darcy was the last man in the world from whom she would expect such a proposal? And, did she believe he could marry his dull cousin because he would not care anyway what woman he married,
At that stage Lizzie didn't seem to even consider Darcy having any romantic interest in her, so yes, I think she was shocked and more doubting what she was hearing because her own dislike of Darcy (particularly after Colonel Fitzwilliam's disclosure) would not have her imagining such a proposal.
But there also is a definitive declaration that Darcy, despite all his concerns about class, wants to marry a woman , not frolic about with a man. He doesn't try to get her into bed, he wants her to be his wife. In his mind he had saved Bingley from an unfortunate marriage because he considered the Bennets below him and not for any other discernible reason than that. He also declared he had seen Bingley fall in love many times, hardly the actions of a loving pair of gay caballeros? In my view, the most telling reason for dismissing the gay suggestion is from Jane Austen herself. Pride and Prejudice (First Impressions) was only her second novel. Would she, a parson's daughter who read chapters of her books to her family, be likely to have a bi-sexual cavalier for her literary hero? I think not.