In her article, "Culture, Ethnicity, and Assimilation in Anglo-Norman Britain: The Evidence from Marie de France's Lais" Marianne Fisher uses the Lais to show that Normans embraced and took on the identity of their new home in Britain. She discusses how records show that Normans, English, French, Bretons, and Flemings were separate ethnical factions, other evidence suggests that there was ethnic indifference (198). This meant that a flexibility existed within the culture and society that made it easy to assimilate. This was also an indication of the Norman tradition. They were successful invaders and the Normans were always willing to "adopt from and adapt to local culture" (199). This reveals both the success and the failures of the Normans and the Norman culture. Fisher points to several lais in order to demonstrate her point. She starts with Lanval, a story about isolation, but with social status comes a way to reconnect again with kin. Fisher also points to several lais when examining the location where certain actions take place, such as Chevrefoil, where the main action takes place in Celtic Cornwall, and Eliduc, which is set in the neighboring Devon. Fisher suggests that these locations, as well as a reference to Breton sources, points to a unified cultural heritage spanning both sides of the Channel (200).
This is an interesting examination into Marie's work, some of the connections that Fisher makes struggles to be evident. She relies on information and details that are minimal, it almost appears that she is stretching to find a connection. But, I do think that Fisher is onto some thing, especially when she looks at the phrasing and language that Marie uses. My biggest struggle with Fisher's argument is that she doesn't look closer at language and at the materials that make up a culture, but rather she looks at pieces that can struggle to fit together.
Marie's work has always been interesting and has always been something that is up for scholarly debate, because so little of Marie is known, and so little of what the lais tries to achieve is unavailable to us. And because of this, Fisher tries to fill in the gaps without sufficient evidence, where I would have liked to have seen more connections and a tighter argument.
I thought that Fisher had made a case for Norman assimilation and certain amount of Britainia assimilation by pointing toward the stories themselves. However, I do not know how Fisher may validate that this was Marie's intent upon relaying these lais. I would agree with you that though a connection can be seen it would be insufficient to say that these were the intent behind these stories.