Thanks for the query. Vaginal infection
can occur due to causes like skin to skin contact, using public rest rooms, due to allergy to inner wear etc apart from intercourse.
So don't come to one conclusion just by symptoms.
General conditions like diabetes
etc can increase the possibility of vaginal infection.
Vaginal infection can be a cause for pain during intercourse
Decreased lubrication due to menopause
can also be one cause.
After her infection gets controlled, she can use some vaginal lubricant to decrease pain during intercourse.