All 3 Uses

alternative
in
Pride and Prejudice
(Edited)

Elizabeth, feeling really anxious, was determined to go to her, though the carriage was not to be had; and as she was no horsewoman, walking was her only alternative.
p. 32.8

alternative = other possibility
An unhappy alternative is before you, Elizabeth. From this day you must be a stranger to one of your parents. Your mother will never see you again if you do not marry Mr. Collins, and I will never see you again if you do.
p. 109.9 *

alternative = possible choice
To be sure, it would have been more for the advantage of conversation had Miss Lydia Bennet come upon the town; or, as the happiest alternative, been secluded from the world, in some distant farmhouse.
p. 293.8

alternative = possibility

Definitions:

(1) (alternative as in: an alternative plan)
a different choice or possibility, or describing something that offers a different choice or possibility
(2) (alternative as in: alternative medicine)
non-traditional or non-standard
(3) (meaning too rare to warrant focus)