Baby not wanting as much food

My baby is almost 12 weeks old. She is putting on weight and has just been weighed today, however, I've noticed over the past few days she just isn't into her food. Today is the least amount of food she has ever eaten. I try and feed her either bootle of breast, but after a few minutes she gets fussy. Our Health visitor explained this is normal as she is likely distracted more interested is the world around her. Has anyone else experienced this? Does it resolve quickly? How did you manage it? Just difficult because once she realises she's hungry she is due a nap and also ends up battling hunger and over tired cries. We have resorted to dream feeding as per the health visitors advice.