Potty Training help. Won’t poop outside.

I have a 4 month old puppy. We have had her for a month now and I’m having the hardest time potty training. She doesn’t care about sleeping in the dirty crate and steps all over the pee/poop. She also doesn’t like going to the bathroom outside. She is from a shelter and is used to going to the bathroom in her space. She’s also a very nervous dog and doesn’t love people, except me and kinda my husband. She’s terrified of my 7 year old daughter but that’s a whole different issue.

We also have a pen connected to the crate and she prefers to pee on the floor in the same place (yes I use the enzyme cleaner) So now I started using pee pads. I swore I wasn’t going to use them but the cleaning up the pee/poop off the floor multiple times a day was draining me and now she’s learning to use the pads. I’m relieved but also worried it will turn into long term.

So how can I get her to go outside more? She’ll pee outside 50% of the time but she hates pooping outside and prefers to do it in private, overnight. I’ve tried taking her outside every 15 mins and back in but she holds it. One day I was watching her like a hawk inside and she got into the poop position so I took her right out and nothing and even stayed out for 45 mins and then she didn’t end up going until overnight so that was atleast 8 hours later. I’ve tried on the leash, off the leash, in the same location, long walks, short walks but she prefers to do it privately overnight on the floor or now pee pad. Should I keep using the pads for my own sanity and get her fully pad trained then work on transitioning to outside?

She’s from the shelter and is some type of lab and Jack Russell mix.