You're right about some of the supposed sightings stating she didn't seem to be in distress... good points,
I find the purse on the bridge one of the most disturbing elements..... I just don't leave my purse and not realize it when I am in control of myself.
To my knowledge, the sightings on the bridge don't say whether MH had her purse then or not, though apparently she did in UHall parking lot, and from what I read it was found (mostly) intact in the corner of the Lannigan Field/R.V. parking lot closest to Copeley Road and the jogging track.
Staying with the purse thread, here are the possible ways I see it getting there:
1) she could have left it there by mistake before crossing over bridge,
2) she could have left it there as "collateral" or something before crossing bridge (wild speculation one poster had, imho),
3) she could have crossed bridge, done whatever she was doing, come back to the R.V. lot and then dropped it, lost it in a struggle (again, no evidence of that), or purposely left it behind, but no eyewitnesses reported seeing her coming back across the bridge or at a bank, restaurant, or store,
4) someone dropped/tossed it there during her departure, in whatever form
5) someone dropped/tossed it there after whatever happened to MH (choosing the location by design or randomly),
6) the purse was lost somewhere else, and moved by an unrelated party to the parking lot,
7) it may have been found somewhere else and/or at some other time but reported by finder to UVA police as being found there and then.