What compressor pedal should I get to sound like Julia Jacklin?

Get the MXR Dyna Comp. It’s cheaper than the Boss CS-3 she also uses, and it nails that subtle, responsive squeeze she gets, especially with single-coil pickups like her Telecaster. Set the sensitivity low and output high for a gentle compression that evens out dynamics without killing attack. You don’t need to spend more than eighty bucks.