TAPVR

My daughter was born 2 months ago with a heart defect called TAPVR, she went through a successful open heart surgery and a few weeks after she had a diaphragm placation and g tube surgery, then 2 weeks ago she went to a last procedure, a pulmonary vein catheter and now thanks God she is finally at home. The thing is that before the pulmonary vein catheter she would take almost a full bottle of 40 cc’s but after the procedure she just won’t take even 5 without gagging and crying and getting mad so we have to rely on the g tube, which is great but at the same time frustrating. Does anybody know what could be the problem? Why she won’t even accept the bottle nipple in her mouth without gagging when before the surgery she was doing so great? I would appreciate any tip that help us deal with the situation and I apologize for my English, I moved from south America to this beautiful country only a few years ago and the language still gives me a hard time.