You might consider making walks for exercise only and not for potty. With young puppies, it's usually better to take them to a designated potty spot.
Same exact spot every time. I would even consider putting a little of her poop out there where you want her to go. If you have a yard where you can put an exercise pen, it might be worth it to set one up as a potty pen. We did this mainly because we wanted to teach Gus to go in the mulch and not in the grass, but I've found it really forces him to focus on the business at hand. When he's in there, he knows it's potty time - not play time. When you go for walks take her to the potty spot first, let her do her business,
then walk.
If you don't have your own yard, then I would consider playing inside for exercise and only taking her out for potty (not walks or play) for a week or two. That way, she associates the outside with going potty only. Again, same spot every time. Then back inside.
Like others have said, plenty of praise and treats for success. You might also consider writing down her daily eating and potty behavior (accidents and successes) to help you see the pattern of when she typically needs to go.
My house rules in the beginning were:
IMMEDIATELY after waking in the morning or from naps
Every 30 min* while awake and playing (if not in crate)
10 min after eating
Let us know how it goes, and the more info you provide about your set up and routine, the more we can all brainstorm. Good luck!
*we got him at 7 wks, he's almost 4 months and can hold it about an hour while out of his crate and playing