One of mine is like that; all excited when asked if she wants to go for a walk and then acts like she's on the Batan death march once we get going. Most of the time I can coax her along using my "excited to be walking" voice, but sometimes not so much. To make matters even worse, she's usually the first one of the three to take care of business, so then it becomes "why-am-I-being-forced-to-endure-this-hardship" while being "dragged" around until the other two do their thing.
Things improved after going through obedience training because she is very food motivated, so treats became my best friend for about 6 months. It took another 6 months to wean her off of them while maintaining some enthusiasm for going through the basic obedience commands while on our walks. She's still bringing up the rear, but it's much better.
Assuming that there's no physical reason (sore/tender pads, cold, arthritis), it make take some motivating to overcome her reluctance to walk.
Hope things improve for you and Dory, after all, walks are supposed to be fun!