Exactly correct. Either she bets nothing, ensuring a tie, or something, which ensures a victory if she’s correct. Since she bet something, she should have bet more so as to earn more money.
She had $20,400
2nd had $10,200
3rd had $8,000
The ‘correct’ amount, IMO would be $4,399. That ensures her beating the 3rd place player, even if that player doubles up.