All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
You are not religiously obliged to inform this fiancée that you had been engaged before with another woman. You have not committed a mistake by not informing her and she should not have objected to it.
You have to know that since you have not yet signed the marriage contract with her, she is considered a marriageable woman, so it is not permissible for you to be in seclusion with her, or travel with her and other things that are only permitted to be done with a Maharam.
It is known that the idea of getting to know each other, discussing and the like before marriage, that is widespread nowadays, is nothing but a cause that leads to committing forbidden things. So it is an obligation to close this door [that leads to evil] and whoever wants to get married with a woman, he can ask her for marriage and look at her to whatever would incite him to marry her or abandon her, and then he should stop seeing her and talking to her until he signs the marriage contract if he is interested in her.
Allaah knows best.