My guess is that the woman anticipated you would stay in the shoulder, going the same direction as her. If I read your account correctly, it sounds like you meant to stay on 14 (not head onto Spur Road) by crossing the off-ramp in front of her. She may not have anticipated this.
What I have found to work well in those situations is to move slightly out of the shoulder WELL in advance of the off-ramp, and watch for a gap. It is really hard for a driver to anticipate which way you will go, and few will slow down to bicycle speed behind you to find out. Those gaps in traffic are critical. And if one doesn't appear, stay in the shoulder until you are just in the off-ramp (where it starts to split off the highway), then stop and wait to cross at a 90-degree angle to the roadway (i.e., the shortest distance possible to cross the off-ramp).