Breastfeeding & dummies

If you are exclusively breastfeeding your baby, how do you feel about dummies?

I've bought one today and am considering using it when my girl refuses to settle at night. Some days she doesn't get much sleep during the afternoon because that's when she likes to cluster feed and then at night she gets so worked up because she is overtired and only settles on the breast but will then overeat and end up even more upset because she is spitting half of her milk up again. I'm hoping that in those moments a dummy might help break that cycle and help her fall asleep.

I'm just afraid that it will interfere with her feeding and as a consequence, my milk supply. She is 5 weeks on Saturday and feeding has been well established.

Anyone with good/bad experiences using a dummy while breastfeeding around this age?