She wasn't though. He had a better hand until the river card was turned over. Unless you mean if she could see not only his private cards, but also the turn and the river. But that would require collusion with the house.
No he didn't have a better hand. He may have had better odds to get the cards he needed to win, but he never had a better hand.
Pre flop:
he had 87s
she had j4o
She's ahead. J high beats 8 high.
Odds might be in his favor but if the board doesn't improve for him, she wins.
Flop is 10 10 9 with 2 clubs
She still has the winning hand (her J high beats the 8 high he's holding)
he has a great chance to come out ahead if he hits his club or straight draw. the odds are good for him with 2 cards left , but again right now she still has the winning hand if he doesn't find a club or straight
Turn is a 3 of hearts (10 10 9 3)
Her J high is still winning vs his 8 high at the moment
at this point the percentages are still in his favor with card left since any club, J,7, or 6 can give him the winning hand(straight or flush) but at the moment she is still ahead with J high vs 8 high since they're both playing the board
River is is A of spades (10 10 9 3 A)
now its official that if he can't get this bluff through her cards of 10 10 9 A and J from her hand beats the
10 10 9 A 8 of his.
He had better odds till the river but he never had a better hand than her. It was always his 8 vs her J.
Because she was able to see each street before deciding to bet or call, she only had to know his hand to make the right decision on each street.