She really should do the LP to rule out mimickers of MS (such as Lyme).

Look up the MacDonald Criteria for diagnosing MS. If she qualifies for that, and all other mimickers of MS are ruled out (such as Lyme, Sarcoidosis, tumor etc.) then she should ask the doc why he isnt diagnosing MS.

MS treatment is no walk in the park, so you want to be pretty certain about the diagnosis.