Since she has been traumatized by the death of her friend's husband, it will take time for her to come out of this fear psychosis.
You may have to wait for her return or attend her daily at your in laws place, make her feel comfortable and try to spend your quality time with her while she is at her home.
Do not insist on her return or urge on it.
Let she spend some more time with her parents and in the meantime ask her parents to take her to some psychiatrist for treatment and relief.
Patience is the need of the hour that you have to adhere to now.
Do not rush up with legal action so soon, this may jeopardize your reconciliation efforts