The women remain undefeated but will be frustrated that they could only put one past fellow San Antonio school OLLU.
UIW dominated the match but finishing and superb keeping from Gabriela Lopez, who made a half dozen saves, kept the score line down.
It was a dominant display from the Cardinals in a scoreless first-half as they looked dangerous, if venom less in attack while also holding the Saints shotless throughout the half.
The second half was much of the same as UIW controlled the match but struggled to put away the plethora of chances that they created.
The goal that always looked like it would come finally came in the 67th minute as Sydney Solomon found Kathryn Mundy in space allowing her to hit a powerful strike from the edge of the area.
UIW controlled the match for the rest of the way but Lopez remained impressive in the OLLU goal, which allowed them a chance to equalize in the 88th minute only for that effort to be denied by Heather Kowalik.
The result is pleasing for both San Antonio schools as OLLU will be pleased to have pushed an NCAA Division 1 school all the way while UIW go 4-0 for the first time since 2001.
For the men it was yet another 1-0 loss as they fell to Duquesne in the final match of the Duquesne Invitational in Pittsburgh on Sunday.
It was a really frustrating match for the Cardinals yet again as they dominated the match, easily leading the shot count and creating plenty of chances while holding out the Dukes but they couldn't capitalize on such heavy domination.
It was one of those matches that was always going to end in heart brake and in the 84th minute Josh Ellis tapped in the rebound from Colin Phillips free-kick to seal the 1-0 win.