I am definitely too nice. I've had students like her before, but this is an extreme. I usually don't have too much of a problem. Of course, I'm not at all trained as a teacher, so there's that
I get it. I've been there.
If I were you, I would have a serious talk with the whole class (no need for one-on-one with your problem student) and lay out some basic rules. No questions until question time. No interrupting without being called upon. Respectful listening, for everyone.
i would take 5 minute at the beginning of the next class to get the dynamics back on track, and then just keep enforcing. ignore your problem student. If she interrupts, say "Susie, I know you have something to contribute, but it isn't your turn yet." " Susie, you're going to have to wait until. Janey, Bobbie, and Jimmie are done talking." "Susie, I'm afraid we don't have time to discuss your past vacations today, if you want to talk to me in office hours, I'm available on Thursdays." Etc, etc.
it should only take a class or two to "fix" this - once the others figure it out, they'll help make the overall atmosphere less conducive to disruption, while still feeling that you're in control of the classroom.