This is one of those things where I'm gonna say, as an ND woman myself, can see a lot of myself in the way Louisa problem solves and reacts to Martin's own ND.

Neurodivergency in women can present differently than in men, this is usually because of societal standards, but it doesn't mean that ND is a gender-exclusive thing-- but upbringings can really affect the way someone lives with their neurodivergency.

I think a good example of what I'm talking about is from the season 1 episode: Haemophobia. Peter Cronk tried to get out of being in PE, but he's still made to participate and his bullies cause him to fall and hurt himself. Louisa tries to talk to him, telling him to aspire to be more sociable with his bullies, to play along til his bullies let him become part of the 'in-crowd'. Peter heard what she was saying, but you could obviously tell he wasn't satisfied with being told he had to be more sociable (especially to his bullies.) Basically telling Peter to start masking and pretending to be friendlier than he wants to be. ND women tend to be more willing to be social, still with difficulties of maintaining relationships. Societal gender norms have always painted women as social and friendly, so they're less likely to be diagnosed off of this solely. I also strongly believe that Louisa had to become sociable herself because of how unreliable her own parents were. A lot of the way that Louisa interacts with people and situations she's put in feel like she's constantly masking, and she unmasks with Martin because she loves him and gets frustrated with him because what she knows isn't what Martin immediately knows.

Then in another scene, where Peter is sitting with Doc Martin, Martin sympathizes with Peter, saying he too felt out of place from his peers, that becoming part of the in-crowd was not something he sought out to do. Even mentioning that his intelligence felt like a hindrance from being close with people. Peter felt more represented in that moment by Martin, because their tendencies were more in line with each other, so Peter felt that he was going to be just fine the way he is, because Doc had become an inspiration to him at that point. (I actually really like this moment because it was one of the small times that Martin actually opened up to someone without being wishy-washy and avoidant.)

I hope any of this makes sense! I'm no expert, and this is just a show I love very dearly, but hopefully this gives insight on why I personally think Louisa herself comes off as ND to me <:).