A few quick tips
If its really nutrients you are worried about, just supplement, it will give you peace of mind.
Breakfast cereals are fortified by law, as are cereal bars. Margarine is as well with the important fat soluable vitamins, though she is probably getting these from her milk. This will prevent things like rickets.
Iron can be tricky with picky kids (which is why I get a bit defensive of the parents who chose to use follow-on or toddler milks - if they are not chowing down on minced beef and curly kale where the fuck are they supposed to get the iron from, and the "healthy balanced diet" argument sort of falls over).
See if you can ensure she is getting the good fats (long chain polyunsaturates - i.e your Omegas 3 6 and 9) - they are important for brain and eye development and the body cannot make them, you have to get them from diet. Once again a reason to have the follow on milks as they are supplemented with this but no, I promise I dont work for a formula company, but have a nutritional qualification which makes it hard for me to ignore the fact that these milks tick so many boxes in one fell swoop that unless you have a "good eater" and a good knowledge yourself, they simply might not otherwise get. No, they dont NEED it but hell its useful and easy if you dont mind paying for them. Having said all this I give mine cows milk from 1 but I have "good eaters" (or did - my 3 year old is now a bit dubious) and a nutritional qualification and a professional cookery qualification and slot together a balanced diet very easily from this kind of info stored in my (otherwise useless) brain.
Your HV can get you a script for vitamin drops for free if you want.
Pity she wont eat fruit, that's a nice safety net in terms of antioxidants and fibre if you do have kids who wont touch veg.
What else. Hang in there, keep offering it, that is really your only "job" is to offer a wide variety of nutritious foods.
Also, in my experience if kids were not picky babies but became picky as toddlers, I find they "come out of it" eventually as long as you carry on as normal. If your baby was "born" picky (some really genuinely are I kid you not) then its going to be more of a slow burning battle.