There are chances that she may feel somewhat uncomfortable outside, or perhaps there are too many distractions going on, and she can't seem to focus enough to relax and poop. Pooping in dogs requires them to be a bit in a vulnerable position, and it requires a bit of concentration. It could be she wasn't well housetrained in her previous home too.
In any, case, it's important to make sure she has ample of opportunities to poop outside. Taking her on a walk may help as motion helps trigger dogs to have a bowel movement. It also helps to feed her on a strict schedule so that she poops predictably at a certain time and you can take her out at that time.
If she fails to poop outside, make sure you keep her nearby the door in an unobstructed view area so she can't sneak in a bedroom or behind some furniture to poop. Keep an eagle eye on her. This way you can promptly escort her out as soon as you notice some pre-potty signs (circling, sniffing, lowering her bottom).
It may help, if she has an accident, to collect the poop and place it in the designated area, you want her to poop outside. This way she can smell her poop there and hopefully help her recognize where her new "bathroom" is.
Also, never punish a dog for pooping inside the home. This only leads to dogs associating pooping in front of the owner as punishment. This means the dog will always sneak in a secretive spot to poop so that the owner won't see them poop. This may also interfere with pooping outside in front of the owner.