Can you help me with this grammar question??

<p>The question goes that way:
In 1961 Rita Moreno gained fame and won an Academy Award for her portraying Anita in the film adaptation of the groundbreaking Broadway musical West Side Story</p>

<p>This is an error identification question in which "for her portraying" is the error. I assumed that it was the error since it didn't sound right, but I need to know the rational behind this error. Plz help and thnx!</p>

<p>portraying of Anita, here portraying is a gerund
my 2 cents</p>

<p>I think it should use a verb like “…because she portrayed…” instead of “…for her portraying…” .</p>

<p>Either ‘for her portrayal of Rita’ or ‘for portraying Rita’ are acceptable. The reason for this is not easily explained. Here’s the brief version.</p>

<p>The sentence deals with the REASON for the award. The reason was not Rita herself, it was her performance (portrayal). Since the word that names the reason is the object of the preposition (for) it will be either a noun, a verbal acting as a noun or a pronoun in the objective case. ‘Portrayal’ is a noun and could be used with the word ‘her’ clearly and unambiguously acting as a possessive pronoun identifying which portrayal. ‘Portraying’ is a gerund acting as a noun and could stand alone without any modifiers and still have a clear meaning. However, adding the word ‘her’ to ‘portraying’ muddies the water, so to speak. Was the award for ‘her’ (Rita) - in this case ‘her’ acting as a pronoun in the objective case and ‘portraying’ becoming a present participle acting as an adjective modifying ‘her’ (Rita)- or was it for ‘her portraying’ with ‘her’ acting as a possessive pronoun unnecessarily added to identify who is portraying. I hope you can see that ‘her’ in ‘for her portraying’ is both unnecessary and ambiguous and should be left out.</p>