not proficient enough to...?

[ph2004]

Is this a correct usage of the word "proficient" : "Her English was not proficient enough to understand him." ?

[Khosro]

I learn English and at the same time I teach English.
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No. Your sentence is grammatically wrong."Proficient" is an adjective for persons.
So you could say:
"She was not proficient enough in English to understand what he said"

now it is grammatically correct. But about the meaning.... I guess there are better ways to convey such a meaning.
you'd better ask a native speaker of English in the forum. What I suggest:

"She was not good enough in English to understand what he said"
"Her English was not good enough so she couldn't understand what he said"
"She didn't know English well enough so she couldn't understand what he said"