Yeah the vet is going to be my best suggestion as well. I've heard they can give an injection that will cause contractions to start again which may enable her to pass them on her own. Otherwise they may be able to manipulate them out or possibly even draw the fluids out of the slugs to enable her to pass them. I have heard of boas (BCi) that held onto slugs and the owner didn't know, they ended up passing them the next year with the litter (they were smaller, dried up compared to the 'regular' slugs) but I don't think I'd chance it.
I lost a boa that was slug bound, the slug was too large for her to pass which we didn't find out until the xrays (I posted about it here:
http://www.faunaclassifieds.com/foru...d.php?t=176477)
Sounds like your situation is different as mine died because she still had live babies inside her that passed and caused everything to go septic but still, better to get it checked out sooner rather than later.
Good luck I hope everything turns out okay!