She has no right over yofr forcing you to marry her.
In a live in relationship, as the name suggests, the relationship can break up and do not have to last longer or has to end up oly on marriage.
It is just that two opposite gender people liked to live with each other till the time they wanted and after that if either or both do not want to continue their relationship, there is nothing in law to force them to be together after that also.
If she continuously threatens to commits suicide then you may lodge a complaint with the local police about this and can inform the police that you cannot be held responsible for any such event that may happen as threatened by her.
You dont respond to her calls. You can block her number in the phone. You can delete her Facebook account, You can discontinue your email account and can open a new account. Take all the steps to avoid confronting her in any manner.