How tiny is "tiny", rickman?
For comparison: my DD is 3y+8 months, she didn't start wearing 2-3yo size clothes until a few months ago, she weighs just over 13 kg (2stone 1lb, or 29 lbs).
Another thing, did you notice with your other kids a big drop-off in appetite/slow-down in growth between approx. 2y+10m & 3y+8 months? Both of my older 2 did that, DD didn't hardly eaten anything after 4pm for most of the last year or so, but she is finally starting to develop an evening appetite, again. I know another MNetter who was complaining the same thing about her DS. May be partly the age, this growth plateau/appetite fall off, I mean.
Anyway, most days I let mine have 1 bag of crisps (or plain hula hoops)/day (Sainbury's do crisps cooked all in veg oil). The salt isn't wonderful for them, but we don't salt the rest of our food so I reckon it's ok. I don't know why people fuss about chips being so "unhealthy". They can fit in a healthy diet fine, and little kids need fat.
One of our local butcher's does quality chicken nuggets, all "real" ingredients. Expensive, but might be worth looking out for. I suppose in your place I'd give in and let her have the supermarket chicken-nuggets once a week or so.