It would be really hard to give an accurate answer to this question without knowing how old your daughter is and whether she has any other health problems or special reasons why she is underweight. If she is a very small child, you should certainly ask your doctor about her weight and whether there is any cause for concern; the doctor can also advise what foods are best.

If she is older, the question is whether she is dangerously thin or just a bit light? If you haven't already, you could put her details in this chart - if she proves to be dangerously thin, again this is a case for a doctor and not just a change of diet. It's really not a good idea to force-feed a child on fatty or starchy foods to try and increase their weight; if you give her a balanced diet with plenty of protein, fruit and vegetables, she has a good appetite and still is really thin, this may be no problem; but you should still see a doctor if you are worried.

If this doesn't answer your question, please do write again with more details, such as your daughter's age etc.