Yeah it's not that sharp of a dichotomy.
It really isn't, no.
Many of her "adorable" comments still come up even if you harden her. For example, in Orzammar you can talk to that dwarf who seems very eager to go and study with the circle of Magi. If you have Leliana with you, she will comment on how adorable the dwarf is, regardless if you hardened her or not.
The only thing that changes if you harden her is that she realizes that her time with the chantry, while peaceful, was ultimately boring and lacked the excitement that her previous life had.
She does not become bloodthirsty or evil in any way. If you listen to her party banter with Zevran, she specifically says that she does not enjoy killing, but the hunt itself (investigating, gathering facts, sneaking around, etc) is fun. It's like riding a rollercoaster. Sure it looks dangerous or frightening, but it's fun! Nothing wrong with that.
She still remains as sweet and adorable as the first time you met her.
Same applies with Alistair.