I think if she's already using the pads indoors, that's great! If you know there's a certain time she usually goes (will take some detective work and time recordings hehe), then take her outside before her usual pee. When they gotta go, they gotta go. And the praise like crazy if she does it outside, with a "good girl pee pee".
I find with mine, if she's running around a little bit, it'll stimulate her to go pee.
But at 4.5 months old, I wouldn't rush it. Make sure she has all her shots etc first before going outside. And don't let her out unless she's on a small harness and leash. My worry would be other animals and eating something bad outside that might get her sick.