If the sister was SUCH a threat... after her recapture she would have either been chemically lobotomized or "put down", not locked up in the same place she escaped from multiple times because "she is in a place now that we can't reach her " or whatever twaddle was said at the end.
Wasn't she in charge of the place, though, because she'd got control of the governor bloke? Although I found that 'She influences and takes over everyone who she talks to' stuff seriously hokey.
How did they do the phone calls with the little girl if it was all a metaphor for Euros' madness?!
It wasn't all a metaphor. Euros had a throat mike, which presumably enabled her to do the little-girl voice. She WAS really talking to Sherlock on the phone; it's just she was in her cell and then at the family home, rather than on a plane. THAT bit was a metaphor: being her is like being on a crashing plane where everyone around you is unresponsive, i.e. she feels totally alone. We saw the scenes on the plane but obviously Sherlock et al didn't; they only heard her talking, and assumed she was on a plane.
I think Molly was consigned to being sad and lonely because that's how Moffat and Gatiss think of women –if you're not a sexy dominatrix or a kickass assassin, you're weepy and needy, mousy and uninteresting.
On that point, I found it quite a leap that Molly was, in this episode, mooning about her flat crying over Sherlock; why were we asked to believe/accept that, introduced as abruptly and lacking in context as it was? In the previous episode we saw her being perfectly functional, professional and normal, examining Sherlock and giving a medical opinion.