This is probably a no-brainer once you think about it but I see it happen a lot with students. If you open right in front of an escalator, it is a disruption. People tend to not want to block other people and therefore she has pressure to move out of the way. This combined with a day game non social environment makes it twice as hard to stop a set. You want to stop a girl right away during the opening otherwise you end up following her around like a creeper.
If you anticipate her heading towards an escalator or the entrance of a store, either run and catch up to her BEFORE she gets to the escalator (at least 15 feet prior) OR you keep your distance and wait till both of you are off the escalator, walk another 15 feet and THEN approach.