My baby is 11 weeks old and has been exclusively breastfeeding since birth. I'm getting my hair dyed on the 22nd and this will be the first time I am leaving her. I will be gone for around three hours. I will express and leave her with my partner. My question is do I need to get her 'used' to the bottle beforehand? I.e should I start giving her a bottle of my milk everyday to get her used to it? Also how much should I leave her for this time? Thanks.