suggestions from my days as an occupational therapist, now retired.
Focus on something other than the walking, so instead of saying, lets go out to the car, talk about where you are going in the car, if the destination is the bathroom or loo, talk about nice talc, fluffy towels...anything really related to where you are going. Similarly keep reli's attention up and ahead..point out a picture on the wall, for instance.
If its possible (and it may not be) mark a wide line along the floor in a contrasting colour that flows through the doorway or other sticking point.
Next one sounds silly but it works...sing something that she can walk to the rhythm of, get her to join in if she can.
If she does "get stuck" try getting her to mark time on the spot then say "One Two Three, GO" or get her to do a LITTLE rock forward with each count.
If you are going to do either of the last two, then you need to get her "ready" by saying something like "okay xxx we need to get you unstuck, let march on the spot....ready one two, one two"....when she is marching then "are you ready? one two three go" Use a similar "script" if you are going to try the rocking technique. Think of the way a child rocks as she (he) gets ready to jump into a turning skipping rope. Rocking is a bit riskier, I would try the marching on the spot one first.
if any of these "tricks" are going to work, they will work better with practice, so if you have any success at all, then persevere.