I don't think you should help her by just giving her the money. But if you want to offer her some extra opportunities to EARN it, then I think that is fine. Sounds like so far, she hasn't DONE anything to save up except not spend what has already been GIVEN to her. While it is a great exercise in patience, it isn't teaching her to WORK for what she wants.
Our kids have certain things they are required to do "just because" they are part of our family (plates in the dishwasher after meals, taking out the kitchen trash, setting the table, cleaning their rooms, putting away laundry, etc). And things they earn "commissions" on (cleaning the bathroom, taking the bins to the street on trash day/bringing them back after the trucks have collected it, vacuuming, pulling weeds, sweeping the front porch, mowing the yard, etc).
I would make a list of items your daughter could do to earn extra $, and list beside each item what you will pay her to do them. Then let her figure out what she is willing to do to earn the money. And I would NOT make the list enough to cover the entire $10 either in one session. Make it where she has to plan: Vacuuming the house ($1.00? - not to be paid for more frequently than every other day); walking the dog once a day for several days ($0.50 per walk?); scrubbing the toilets ($0.50 per toilet?); pulling weeds from the flower bed ($2.00?); etc.
She will feel such pride at having actually EARNED the money! AND, it will give her a new appreciation for the value of a dollar, something sadly lacking in a lot of kids these days (my own included).. seems all the extended family and friends tend to give $ or gift cards for special occasions and they always have something handy to spend on any little thing without having to work for it.
I think the reward she gets for saving for the doll should be the intangible life lessons she is learning, not the rest of the money.