>>280232953
Frieren is a law abiding citizen and does not want to get in trouble with various lands laws. Beyond that, if you really ask, "who would stop her if she tried to force her way through?" the answer is still no one because Serie doesn't care if Frieren wants to go put herself in danger, but Serie easily could if she felt like it and there's nothing Frieren could do about it.
>>280233036
She's not as bloodthirsty as you think. Frieren was willing to let Aura walk at the start, after all. And her plan with Macht was just "let him die of old age in the future".