WHY does Angellica fall in love with Willmore? Doesn't she know better in The Rover?

If you ever understand the science of love and falling in
love, you will make millions!  No one can make themselves fall in love with someone
he/she doesn't; by the same token, you can't make yourself not love someone you do.  If
we could turn it on and off like that, the wonder of love would be lost.  There would be
no challenge or conquest at all to the "battlefield" of love (Pat Benetar referred to it
in her famous song).

Angellica is a courtesan who makes her
living and satisfies her desire for a lifestyle of wealth and comfort by marketing her
body to rich men.  This lifestyle is a matter of survival for her, so to fall in love
with anyone would be the end of her life as she knows it.  She not only enjoys the
wealth of her lifestyle, but also the control she has over these men.  If she fell in
love, the shoe would be on the other foot...she would no longer be in control.  However,
as I mentioned above, we do not get to choose with whom we fall in love or when it will
happen.  Quite possibly, she had no choice in the matter when she falls for the
Captain.  Fortunately for her, Don Antonio takes her in so that will no longer have to
advertise her wares to make a living.