What is the ruling on lying to those who interfere in one's personal life and whose interference is unwelcome?

Lying is forbidden and is not permissible except out of necessity or a legitimate need that cannot be fulfilled otherwise.

One should not lie to repel the intrusion of others. Instead, one can use allusions (ma'areedh) or tell them frankly that "from the perfection of a person's Islam is his leaving alone that which does not concern him."