Won't take the bottle

I have been exclusively breastfeeding since week 11. Prior to that I was pumping and feeding with a bottle. Today at 20 weeks I tried giving my daughter a bottle of expressed milk and she wouldn't take it. She would even spit out the milk that dropped into her mouth. So I put her back on the breast with no issues at all and tried later with no success. Between my mother-in-law trying first, then my husband, and then me, she completely refused the bottle. Is this just a phase and if not, how do I get her to take the bottle again in case I need someone to watch her for a few hours?