Friend upset that baby prefers dad

My friend is a stay at home mom. The dad took 2 weeks off when baby was born and then went back to work.

Their baby is almost 1 year old and prefers the dad.

He only wants his dad when both parents are there. He is happy with mom but when dad walks in the baby starts crying and reaches for dad. Only dad is allowed to feed him when they are both there. When the baby is upset, only dad can comfort him, when both parents are there and so on.

My friend is very hurt, because she is the primary caregiver.

What do you think?