Hm... Ashley's max level is 40, so you seem to be missing a few events there. I can't remember how many relationship levels you get in the last event, but I don't think it's 4.
Did you use any cheats? Cheating friendship levels can and *will* come back to bite you, unless you know *exactly* what you are doing. And by that I pretty much mean "unless you are Runey", or at least acting under advice from Runey to fix a bug.
Otherwise, all I can think of is: did you get all the college events *and* the bar events for all of them?
Also, you might need the barista outfit for Maria as well.
Anything more than that I think needs Runey's attention.
(Edit: thinking about it, the cheat option is the most likely to have broken stuff, so I moved it up for readabilty)