But Dorrimore struck her as more sincere than the rest.

Besides, he was very good looking.
Lavinia couldn't help having admirers.

Nature should not have endowed her with such alluring, innocent looking eyes, with so sweet a mouth.
She had always had some infatuated young man hovering about her even when she was her mother's drudge at the coffee house in Bedfordbury.
Perhaps she inherited flirting from that buxom, good-looking mother who had the reputation of knowing her way quite well where a man was concerned.
"Archibald Dorrimore will be _Sir_ Archibald some day," she mused.

"It would be rare to be called her ladyship.

I can hear the footman saying: 'Your coach is waiting, my lady.' Lady Dorrimore--how well it sounds! Archibald loves me...." May be this conviction settled the matter.