Thank you for your query on Healthcare Magic.
As she is low percentile for weigh, the organic causes for her vomitings should be investigated.
Forceful feeding also one of the cause for vomitings in this age group.
The other causes of vomitings like intestinal like reflux and obstruction, metabolic, thyroid
, and neurological should be ruled out by physical examination and with investigations.
Consult the pediatrician
for this problems, get examined and investigated thoroughly to rule out any underlying medical problem for her underweight
Hope I have answered your query.