Anti-Anxiety Med for ALS Patient

My mom was recently diagnosed with ALS.  She was already on Celexa for anxiety...she's taken it for years and was happy with it.  However, the neurologist said her recent diagnosis has caused much more anxiety (which is true).  He said that Celexa is too weak and may aggravate the restlessness in her legs.  He started her on Effexor.  One week of 37.5mg went fine.  Then she started the week of 75mg...she has gotten tired much more easily and earlier in the day.  She is concerned about continuing the 75mg, and not willing to go up to 150mg as the doctor prescribed.  We read that Effexor can cause fatigue as well as other side effects that would not be helpful to someone with ALS.  My question is if there is a more appropriate anti-anxiety med for people with ALS.  Or, would Effexor be effective at just 37.5mg?  Thanks!