There might be two distinct ways to describe Gilbert's work in light of feminism. A conventional read through the lens of feminism might suggest that Gilbert did not need to conform to social expectations in order to find her voice and happiness. Gilbert finds herself in an unfulfilling marriage and a relationship that was not satisfying to her. She embraces a feminist notion of success when she is able to find her voice devoid of a patriarchal structure. She does not need a marriage in order to be happy. She does not have to be a part of the structure that silences women's voices in order to be accepted. Gilbert's narrative is one where she is able to find her own voice, and as a result she embraces an aspect of feminism in that she is the author of her own narrative. Gilbert demonstrates an aspect of agency that is a significant part of feminist discourse.
Another read on Gilbert's narrative could be one in which feminism offers a significant challenge. Gilbert's struggle to find voice does not result in any social cohesion. She is not en route to doing something that seeks to establish voice for women in general. Her narrative is one steeped in individualism, something that feminism repudiates. Feminism sought and seeks to transform "lives of quiet desperation" into something more collective. Individual voice is measured in how many others are reached. Gilbert's primary insistence is in the realm of the subjective, and while she might be articulating something that other women can do, the emphasis is personal as opposed to subjective. This might be where a feminist analysis of the work could take place.
I would also suggest that a strong feminist analysis might focus on how Gilbert had her publishing company pay for her voyage. Her agency only goes as far as the publishing company goes. This might be where a feminist challenge could be launched. Gilbert "finds herself" in so far as she is able to from a multinational corporation. This privileged position of wealth might not be applicable to all women.