Your bluff with the swamp was a good move, but Momilani may have sealed her fate when she cast the Fascination and gave you more options. Strangely enough, although she does have a solid enough defense to stand in the way of your creatures, her Destructor Dragon is likely to be the source of her demise.

1. Tap two plains to add (one used as generic mana), two mountains and Wind-Scarred Crag to add (two used as generic mana), and three swamps and Bloodfell Caves to add  (two used as generic mana) to your mana pool.
2. Spend to cast Siegecraft on Momilani’s Destructor Dragon. Destructor Dragon is now a 6/8 creature with both Fruit of the First Tree and Siegecraft attached.
3. Spend and sacrifice Rotting Mastodon to cast Collateral Damage. Choose to have it deal 3 damage to Momilani’s Jeskai Sage. Jeskai Sage dies. You now have 8 cards in your graveyard.
4. Jeskai Sage’s ability triggers, and Momilani draws a card. Momilani now has 8 cards in her hand, and 22 cards remaining in her library.
5. Declare the start of your combat phase, assigning your Mardu Blazebringer to attack.
6. Momilani may choose to block your Mardu Blazebringer with either her Summit Prowler, or her Destructor Dragon, or both, or she may choose to absorb the damage. If Momilani chooses not to block, the Blazebringer deals 4 damage to her, and Momilani is now at 11 life.
7. At the end of your combat phase, sacrifice Mardu Blazebringer. You now have 9 cards in your graveyard.
8. Spend and exile all nine cards from your graveyard to cast Dead Drop. Choose to have Momilani sacrifice two creatures; she is forced to sacrifice her Summit Prowler (if it is still on the battlefield) and her Destructor Dragon.
9. Destructor Dragon’s ability triggers, allowing Momilani to destroy a noncreature permanent. Momilani may choose to destroy any land or your Brave the Sands; the choice does not matter. She is not able to destroy either her Fruit of the First Tree or your Siegecraft, as these are destroyed when Destructor Dragon is destroyed.
10. Fruit of the First Tree’s ability triggers. Momilani gains 8 life, and draws 8 cards. Momilani now has 16 cards in her hand, and 14 cards remaining in her library.
11. Spend to cast Dark Deal. You discard three cards (Goblin Heelcutter, Scoured Barrens, and Temur Battle Rage) and draw two cards. Momilani discards 16 cards and draws fifteen cards.
12. Momilani draws each of the last 14 cards remaining in her library, then attempts to draw from an empty library on her 15th draw, and is defeated as a result.