You can give her poly-vi-sol [liquid vitamin you can find anywhere], but make sure you read the label, because as far as I remember, the Target brand did not have iron in it. I know the Enfamil brand does though. Poly-vi-sol is made for infants.
All of those gummy vitamins do not contain iron. I checked every brand at Target!
Another option is buying her Pediasure, or a toddler formula. My son was on a toddler formula along with whole milk until about 16 or 17 months to give him the iron he needed and because he was not ready for the kids vitamins yet. I thought about trying the poly-vi-sol, but it comes in a dropper, and he always fought me like crazy when I was trying to give him medicine. So anyway, the toddler formula worked for us.
Also, he is now 25 months, but still can only have half of a vitamin. Usually the kids vitamins say age 2-4 can have half, and 4 and up have 1 vitamin a day. My son was the size and weight of a 2 yr old at 17 months, otherwise I would have continued with the toddler formula, because certain vitamins can cause a lot of damage if you overdose -including iron.
ETA: Another option is, if you think she will eat cereal on a regular basis, you can give her fortified cereals, or foods with high iron contents. Barnum's Animals Crackers have as much iron as spinach [which actually is still not very much- 6%] and meat and veggies, beans, raisins, apricots, dates, etc. Vitamin C helps the body absorb iron, too, so if you pair it with a fruit or fruit juice she will get the most out of it