I'm exclusively breastfeeding my 2 month old daughter. How do I know if she's already finished eating?

Per my wife who has been breastfeeding my son since he was born, the sign that a baby is done feeding is when he/she unlatches. That's all. A baby may take a break or fall asleep while being latched, but that doesn't necessarily mean s/he's finished feeding. Breast compress when a baby has fallen asleep and when he/she unlatches, you're good to go.