Holding the bottle near the caregiver's breast may help, but some folks are sort of squicked out by that idea for some odd reason. On the other hand, if the caregiver is already holding the baby in the position you normally use, have her try something slightly different. Maybe baby is mad because, when she's held that way, she expects a Mama breast. Have the caregiver offer the bottle at a time when baby isn't ravenously hungry. Try to feed when baby starts getting drowsy or when she is just beginning to wake up.
Some babies seem to adapt best to the bottle when sleeping.
Have the caregiver just pop the nipple into his mouth when he's asleep, and often he'll take in a couple of ounces that way and become more forgiving of the dreaded artificial nipple. Encourage nighttime nursing during this trying time. Lots of babies just reverse-cycle in the early months, choosing to sleep away the day and nurse all night. My son did this in the early months after I went back to work. Mom should not be the one giving the bottle.