use a slow flow nipple when bottle feeding?

kuipo324

my LO is 4 months, so i was trying to use the medium flow, and was thinking of using the fast flow since i have a fast letdown. but does that matter? she is refusing bottles all together so im trying everything. just ordered the lansinoh momma bottles with medium and fast, im anxiously waiting for them to come in the mail.. but maybe i should order the slow. is it better to go back and forth to breast with a slow flow nipple?