try the organization sponsoring the mission trip and ask for their guidelines on how to get support.
approach organizations whose goals are in line with that missionary effort.
try Catholic Daughters or NCCW or your local Altar Society or other Catholic women’s organizations, for instance there are several women’s orgs. in our old diocese tied to various ethnic associations.
also approach professional or work organizations of you and your husband which may support youth work.
try any organization your daughter has ever belonged to, scouts, Y, 4H, key club, NHS etc. particularly those that are big on community service, they may provide partial support.
is there an organization that has ties in the area where she will be working that would support efforts there?
we have youth who come here every summer and work on the border, both here and in Mexico. One group from Indiana gets money from a local office of a national corp. which also has a plant in Mexico in the city where the youth work on their mission trip. another college group gets funding from the campus ministry.
my niece goes with her church group every summer on a mission trip, and gets money from her father’s employer, which is big on supporting community involvement (her father gets paid vacation to accompany the youth on this trip).