I know Lydia you see Samantha in a relatively positive light, but from my viewings, that statement about her being incapable of love strikes me as being right. That's always the impression I've had of her from the start every time I watch 1840, with the possible exception of the first Samantha scene in the playroom while Julia watches. The picture I get is of someone who has attachments, sometimes fierce ones, but who is cold, and is motivated (not consciously) by the need to hold on to what's hers: children, marriage (divorce was seen as shameful and definitely a huge loss of status).
All people have a healthy human core in them somewhere that can love others, and we may see some of that with her and Gerard (in happier days), but there's also a lot of self-love involved there too, I think. I get the impression that for some people, as far as love goes, they're in it for the flattery from the other party. Gerard could tell, and laid it on thickly.
I try to imagine some sort of genuinely warm moment between Tad and Samantha, and I can't. Her declarations of great love and devotion for her Tad sound to me like "drama", and a sort of feminine equivalent to male macho bravado. While a male might brag about battlefield, sports, or bedroom conquests out of male insecurity, perhaps a female might shout about her nurturing soul and devotion to children, and rail as publicly as possible against her child's perceived enemies (like a conveniently warlock-ish husband), because of her own gender insecurity. Maybe she does love Tad somewhere deep inside, but she's cold on the surface, and of course, the societal requirement is that females be "nurturing" and warm.
These are just my impressions. Lydia or anyone could point out one fact I'd overlooked till now, and it could all come crashing down.
By the way Lydia, did I steal my idea about everything from the start of 1995 on being a separate reality disconnected from Regular Time from you? I think I probably did. Then I acted as if it was some brainstorm of mine...