The court's decision dismissing the petition on the ground of insufficiency of evidence is generally considered a decision on the merits of the case, in which case, the dismissal of the case is considered with prejudice. However, if it is stated in the decision that the dismissal is without prejudice, your friend can certainly refile the case.
Refiling the case that has been dismissed on the merits / with prejudice constitutes forum shopping which means filing of several suits before various courts for the same cause of action in the hope of securing a favorable resolution/judgment in a "friendly court." Forum shopping is prohibited in our jurisdiction. The petition for declaration of nullity of marriage is always accompanied by a certification against forum shopping wherein the petitioner will declare UNDER OATH that no similar action has been filed involving the same parties, subject matter and cause of action. If your friend will declare UNDER OATH that no similar action has been filed, then he/she will commit perjury.
The proper recourse should have been to file a motion for reconsideration of the court's decision within 15 days from receipt thereof or to appeal therefrom. Your friend could have even sought reconsideration of the decision for the sole purpose of remanding the case for further trial IN THE INTEREST OF JUSTICE as it will allow the evidence to be fully ventilated.
In any case, your friend should not lose hope. Philippines Lawyers are resourceful. There are various ways to make things right.