Futaba (Sojiro?) may be autistic but that also clashes with the fact that her traits may be a result of her mother's death. Isolationism is an autistic trait, but shutting yourself out due to bereavement doesn't seem too far fetched either.
Her obsession with technology seems like a hint but, again, doesn't necessarily point to autism. It could just be an interest (she's the "hermit", so rather than having a propensity toward technology she may simply have had too much time to spare and thus learned these skills due to that).
Social skills will be weak when you don't leave a room for years (she's about 16 - 18 but still basically acts like a child emotionally, hiding behind other people when strangers arrive for example). This could be autism, or it could be isolation.
Basically, she seems autistic but may not be that way because of autism. It's really hard to say; most media doesn't explicitly state when somebody is autistic but appears to be (Sheldon Cooper, Fraser, Michael Scott, Dwight Shrewt, etc.) so it's difficult on this premise alone.
Though I'd say if it seems that way, it's very possible.