Hi there ~
I understand your concerns. Crystal meth
addiction can be fatal. I also believe that getting an epidural while being on meth and not letting the doctor know about the addiction can be serious as the withdrawals from the meth is very lethal if untreated. I suggest that you come forth with her history if you are concerned for her life as this is something you could do to prevent any lethal side effects. I hope you understand. Eventually she will need rehab but for the surgery you must let the doctor know of her addiction issues.
I hope this helps. Take care and have a lovely day!