Can't argue really, I realized after reading your post I did get a few things wrong. Timeline of the games, bits of story that slipped my mind from previous games, etc.
Essentially there are two ways to diverge personality from Samus, and Video Game characters in general. There's the story made up of cutscenes, bios, and tidbits of information scattered among the level and then there's user interpreted information garnered from the gameplay. For example, you look at Kratos from GoW and without knowing the story you may not realize why he's so violent or invent other reasons for him to be as violent as he is. Maybe your angers are projected on to him and he becomes one of the worker class who was just about to get that promotion until the rise of some unseen force ruined it for him. You then learn then that he was tricked by the gods to kill his loved ones, holding resentment towards them yet aiding them in order to forget his pains and you understand the character's own reasons for his actions. The Metroid titles, not being overly story driven in the past, have less of this luxary.
From the tidbits and bios, the basics of what we know (or I know, I haven't played fusion and forgot some of which was mentioned in the Prime games) is that Samus was adopted by the Chozo after her planet was attacked by Space Pirates, raised as a warrior, then served in the Galactic Federation before residing herself to the life of a Bounty Hunter. Combine this with the type of gameplay and most would assume she's a fearless "hunter"with little emotional ties. Taking on jobs as a necessity and doing them to completion, like a freelancer who must work for a client wether he or she's invested in it. There's also the possibility that she's more invested in the jobs we play her in due to some emotional tie to characters or events, or species, but most of this is assumed through gameplay. We knew Space Pirates were bad, but why we fought them was up to the player.
With Metroid: Other M we are given more backstory to understand the human aspect of Samus and what drives her emotionally, things we could only assume from previous titles. The writers of Other M gave us, although poorly written, reason for Samus's loner personality. Despite being raised by the Chozo, she's still human and even at times acted irrationally. She resented Adam as an authority figure yet respected him as a father figure. After the loss of Adam's brother decided to leave and become a bounty hunter. What happened between then and the following games is undetermined, but one can assume Adam's example sunk in as she learned to deal with the recluse life of a bounty hunter. That's what I took from it anyway, haven't thought enough about the baby stuff to reach a fully formed response to that yet.
When structured like this, Metroid: Other M actually makes her a better character when you work it into the rest of the series lore about Samus. This actually, in my opinion, does make her a strong female lead. Though if she had some female role models as well as Adam it'd make her even better and seem less like a woman with daddy issues.
So does this assumption clash with what you took from the lore supplied or with what you interpreted from the action and how you played? That distinction is important when judging a characters personality. The writing, though, you can mock as much as you want.