When I get time I want to sift through YouTube videos to see what I can find.
Here it is:
If balloon lady was part of it she would be leading the parade. She passes the striped sleeved lady, stands next to her and lets the two bombers go by. The very second Djokhar passes by, striped sleeve lady begins to fiddle with something in her hand, probably a phone.
Looks intriguing, but could simply be a coincidence. Lots of people walking around, standing around, etc. The timing of balloon lady and striped sleeve lady however, seems odd.
Here is one video showing more “followers” of Tsarnayevs, with backpacks, following in similar distance as the two brothers.