Would the Rose be so powerful without her? Were there any moments when she wanted to withdraw?
the first of these answers would be that the rose only exists because of her in the first place, so take from that what you will. as for the second, whether or not she wanted to withdraw, remember what she said immediately after freezing us:
Jaania: Whatever it takes.
pair this with how much of a knight templar she has proven herself to be as the rose leader, it leads to the conclusion that the thought has never ONCE crossed her mind to back out. when she said "whatever it takes", she MEANT it.
as for how she got akanthus on board, that's something we all want to know still. and considering akanthus is stated to lie to everyone, "especially jaania", i'd say that the manipulation rate is at least 90%, considering the fact that the rose has existed for 5 years, and he's STILL not only on board, but of equal rank to her in the hierarchy, thus implying that none of the rose members(jaania included) ever caught onto his lying.