we had the same problem about half a year ago, she's 21 mths now. it was too easy for the helper to be feeding her watching DVD, bub just opens up like a robot, vs. with the TV off, we need lots of 'entertainment' on the side.
took a bit of insisting from me so my helper won't do that while i'm at work. she still slipped into it when bub is fussy, which i accept once in a while, i understand how much harder it is feeding without it. i'm going on a trip and i KNOW I will succumb to the DVD when i'm much more desperate for her to eat properly on a trip (we had serious poopoo problems on trips... when she doesn't eat her veggies well), i'm still battling this one out in my head.
suggest you can start a meal WITHOUT the TV, maybe pop it in only after other toys and stuff doesn't work, and when she gets really fussy, you might be surprised you might not need it.
we have lots of toys and songs during meal times, we also tried a plain CD where we sing-along, i feel it's a lot better than DVD already. it's not the best that they need all these entertainment, but kids are kids, if you have someone who doesn't necessarily 'enjoy' their food like adults do. also, try to teach her to tell you when she's full, so she doesn't HAVE to finish EVERYTHING, i think like all of us, there are some days when we just feel stuffed and don't feel like eating too much, we let her out of her chair when she says done, so to not prolong the meal unnecessarily. there'll be good days and bad ones... good luck!