some leopard geckos stop eating for a number of reasons.
one reason is often impaction. this is where the gecko has a build up in their stomach which they cant pass, which is often caused by ingested substrate. if your gecko is on sand/calci-sand/anything they could possibly ingest, move them onto paper towels (cost barely anything) immediately. if it could be impaction, try bathing your gecko in warm water for 10-15 minutes - the water can help get rid of impaction.
another reason they may stop eating is they might have just gone off the food. if you feed them the same thing constantly, they can get fed up and not eat. in this time they live off the fat reserves from their tail, which can keep them going for a long, long time. if this is the case, try switching up the geckos diet - mealworms, crickets, and occasionally silkworms or waxworms are all okay.
if your gecko doesnt seem to be acting as normal, they may have a parasite or illness. in this case, the only thing you can truly do is get in contact with a reptile specialist or vet.
i understand money is an issue as it is for many people, but there is a life at risk here essentially. explain this to your parents and try to encourage them you'll work hard for the money spent by doing things around the house and such. if not, call a specialist and explain your current situation - they may be able to give you advice over the phone.
if i am honest, if your gecko is acting normal and doesn't seem thinner, she may be eating with out you noticing. it is always possible, as they do most of their eating and hunting at night, as they are nocturnal.
good luck, i hope everything turns out okay :)