Possible Diagnosis

Just happened to come across a public service ad about PBA -- Pseudobulbar Affect -- and based on Clara's behavior at the swimming pool and description of her condition in the film, I think this is what she suffered from. It probably wasn't understood as well in the '60s.

From Wikipedia:
Pseudobulbar affect (PBA), emotional lability, labile affect or emotional incontinence refers to a neurologic disorder characterized by involuntary crying or uncontrollable episodes of crying and/or laughing, or other emotional displays.[1] PBA occurs secondary to neurologic disease or brain injury. Patients may find themselves crying uncontrollably at something that is only moderately sad, being unable to stop themselves for several minutes. Episodes may also be mood-incongruent: a patient might laugh uncontrollably when angry or frustrated, for example.