7 months rejecting milk

One of my 7 months twin, a girl is rejecting her milk intake. Usually she loves her milk and milk time. Now its so hard to get her to drink her milk. She even gagged when tasted the milk. She will only drink after i coax her into it or after 9-10hrs since the last one. I am getting worried. She has no problem drinking her plain water out of the same size teats and bottle tho. No problem with her solid too but do have issue if the food was a little warm. Is it becos shes teething? I can see her gums getting redder than normal. It has been going on about 3-4days now. I gave her 150ml cos for the long hours. Anyone encountered ae issue with a baby girl? Pls let me know. Thank you.