Both the consitpation and teething could be causing her to eat less. I like Therese’s idea of adding a little more water to her soy formula, or you could add 1/2 ounce or an ounce or Pear Juice once or twice a day. That’s what I did with Myles and it seemed to help his constipation.
For teething I used to give him tylenol or Motrin 1/2 hour to 45 minutes before a feeding and that often helped. On really bad days I’d spoon feed him his breast milk or formula….he usually would accept that over the bottle when his gums were very sore.