If she is not in your videos and she can not be identified by information you provide in them about her (like address/phone number/school etc.) there is nothing to worry about.
If she starts to threaten you physically or in any other dangerous way simply inform the police. They have the autority to request from Google her personal information and to contact her if necessary.
Sorry for what happened.
In general YouTube staff keeps record of previous flags and strikes. If they see that she is unreasonably flagging your videos they will simply stop paying attention to her flagging activities and ignore her.
Just make sure that all your videos are in accordance to YT rules so she has no real reason to flag them!
I really hope so! She has done it 4 times in 2 days!

And all times in vain - I guess!
In anyway if you get unreasonable strike (and you're absolutely sure about it) just go to the official YT help forum and ask some of the TCs (Top contributors) to escalate the issue to YT staff. This usually helps if the strike was indeed unreasonable.