I signed a lease for a condo with another woman. She then started calling the police, saying I was acting weird; she was hassling me because I would not give her money. I was afraid of being arrested because of her allegations, so I moved out and sent the landlord a letter saying it was impossible to stay because I was extremely afraid of the person's conduct, concerned for my safety, welfare and possible false arrest. Does the law permit leaving under such circumstances?
It sounds like you did the right thing, from a safety standpoint, but you won't necessarily be excused from being responsible for the rent.
Until the landlord terminates a lease, a tenant usually must pay the rent unless the landlord fails to maintain the rental in a livable condition. Truth is, it is not your landlord's fault that your co-tenant is dotty.
If you could turn back the hands of time, it would have been better to approach the landlord before you moved out, explaining the situation and asking to be let out of the lease. Most landlords will excuse a tenant if the situation is truly dangerous, but may be less likely to listen to your tale after you've gone and they're left looking for the lost rental income.
Your hope now should be that your former landlord will simply look to the remaining tenant for the full rent, and leave you alone.