Crying after bottle

Melissa • 26. I love my husband and so thankful for my friends & family. We're expecting our first little one.
My little girl is 14 weeks and I'm breastfeeding her exclusively. I'm going back to work soon and I have a nanny who will look after her when I return-because of this, I have been expressing so that she can get use to my little one's hungry/sleepy cry and learn how it will be without me here.
Thing is, she drinks about 120ml at the moment but whenever we take the bottle out she screams like she wants more but stops after she burps. At first I thought she wanted more food but she does it no matter the amount. Should I just feed her more or has anyone else experienced a baby doing this? Is it perhaps because she is comforted by drinking and she just cried because it's taken away?