I agree that she loved the kids, and regardless of how curated those photos on her FB are, the kids genuinely look happy and as if they enjoyed great activities with her. So they probably loved her in return, even if she was scary and unpredictable sometimes. Kids are pretty unjudgmental about parents, so I'm sure they did love her.
However, what would a loving committed stepmother do in her circumstances, if Jason had died unexpectedly of natural causes/ car accident? She's entitled to feel defensive about her financial security if he was the breadwinner, and she's entitled to feel protective of the children she raised for most of their childhood... now the family guardians are proposing to take the children to another country. Surely the most productive and positive thing she could do is negotiate peacefully with the new guardians, explain and demonstrate how much she loves the children and how much the children rely on her for their security. In normal circumstances, an aunty who is grieving for her brother, and confronted with the prospect of guardianship of two small children, would welcome the fact that a stepmother is keen to take at least some responsibility for their upbringing.
If the stepmother lied, encouraged the children to be secretive, made nasty backhanded comments "to" the children on FB knowing the guardians are the ones reading it ("remember I always told you smoking is bad" was one of the milder ones) and tried to cut her husband's grieving family out of the children's lives, I think the family would be very concerned and proactive about securing custody. More so than if she willingly cooperated with them to maintain stability for the children.
