According to Mrs. Gardiner, what did Darcy discover about Lydia's intentions in running away with wickham. what do these intentions reveal about her character?

Lydia is basically out to lunch. She doesn't understand that her elopement would be the ruin of herself and her whole family. She thought they would get married and live happily ever after. She had know idea that Wickham wanted some quick lovin and intended to dump her in a foreign country.