Trevithick scores game-winner in 87th minute.
Bruins score three goals in second half to take insurmountable lead.
Bruins' senior midfielder Jessie Fleming represented Canada at the 2019 Women's World Cup in France.
UCLA will host Loyola Marymount on Friday at 7pm.
Fleming, Sanchez, Parker earn preseason honors.
Four of the last six NCAA Champions will convene at Banc of California Stadium.