Goodness. You've been through a lot. I wonder, as I'm sure you do, if the bile could've caused some physical damage. Of course, sometimes it's just coincidental - the stress of surgery could've triggered Celiac to go full-blown, for instance - but the timing seems too convenient, eh?
One thing I'm wondering about is adhesions. I don't know too too much about them, and it seems like most doctors don't either. But from what I understand, it's when excess scar tissue forms around your organs, often attaching them to each other etc and impeding their functioning. Surgery is one risk factor. I wouldn't be surprised if the bile had caused some scar tissue to form, too. The adhesions would of course be outside your intestines, so they wouldn't see it on a lower GI. I'm not sure how they're diagnosed (perhaps with a lap procedure??) but I think the hardest part of it is convincing your doctor to look.
Another thing that comes to mind is the normal GB surgery complications. For some reason, doctors LOVE to pretend that GB surgery will make you all better, but a small but significant portion of patients end up with just as much trouble as before. Sphincter of Oddi Dysfunction is one common problem. You could have uncontrolled release of bile into the intestines, which could be controlled with bile-binding medications like Questran. Those typically occur when there are no complications. Since your surgery was more, um, complicated - I'm not sure what the full ramifications would be, but I'd have to assume you've got more chance of after-effects. I don't know if a bile-binding resin would help your situation, but it may be something to ask your doc about.
So, your homework assignment: google adhesions, sphincter of oddi dysfunction, and bile-binding

Did you change your diet after the GB surgery? Low fat, etc? Do you know what it was your mother was diagnosed with? At least they're starting to take this seriously, it seems... Keep us posted on here... getting a GI diagnosis tends to be a long process, and you tend to have to inform yourself & do a lot of pushing, but it can be done!!