Mathilde's work focuses on the transformations in rituals and care practices in the context of the recent French departmentalization of Mayotte. This island in the Comorian archipelago is the only one to remain French after independence in 1975. Her research is at the intersection of anthropology of rituals and anthropology of care.

Her thesis looked at care practices in everyday life and the care apparatus mobilized for young afflicted people in Mayotte. It shows how these individual afflictions relate to the social tensions and conflicts caused mainly by the migration of people of foreign nationality and the recent French departmentalization. In response to these afflictions, young people turn to three main apparatus: 1) marriage, conceived here as an alliance apparatus capable of integrating an individual into a community by granting them a change in status and reaffirming their affiliation; 2) affliction rituals, whether Islamic practices or spirit possession rituals; 3) medico-social institutions, which are often state-run or state-funded. While not all young people are afflicted, most of the young people on the island are of foreign nationality because they were unable to travel to mainland France for their studies or to find a job. They are therefore often looked after by the medico-social apparatus. In addition, the gender of the afflicted person also influences the type of apparatus they turn to: while young girls are more easily taken care of by their families in the alliance or affliction rituals apparatus, young boys are more likely to turn to medico-social apparatus.

Her actual postdoctoral project stems from an observation made during her doctoral research: while the pain inflicted in certain rituals (of cycle life and of affliction) in Mayotte becomes intolerable, it is maintained and valued in others. Indeed, pain is maintained in rituals where it allows the novice to move from a passive state of victim to that of agent, and it is abandoned in others. But this study contributes more generally to a reflection on the anthropology of ritual. On the one hand, it shows that, more than the influence of French ideology on this recent overseas department, this criticism of pain in rituals reveals the tensions that exist between the authority of Mahorais rituals and the authority of metropolitan institutions. On the other hand, pain, as a borderline experience of one's bodily capacities and belief, puts in crisis the "serious fiction" (Bateson) proper to ritual, making it more serious than fictional.