If you can't manage 4 hours, then start with 3.

I've had to do it this time around, bit different because I'm tandem feeding (are you still feeding your DD1?) so I actually did 6 hours each boob, but I have a toddler who was happy to clear the other side. Also, my boobs never went crazy swollen when full like last time, I put it down to feeding through pregnancy, and it made oversupply really hard to diagnose.

I did 6, then down to 4, and then started doing 3 hourly feeds from both sides. Going to 3 hourly really helped, and as much as it made me feel like a T.Hall disciple, I'm glad idid it! So, yeah, I say try and hold her off a bit. After about 3 weeks of 3 hourly feeds, we're now happily demand feeding.