Only Jehovah can read those hearts, we as humans can only guess at what is in another's heart.
That is why the separating of wheat from the weeds is necessary, to root out those whose hearts were never inclined towards Jehovah, to expose those who only have a form of Godly devotion. Indeed that is why he will say in that day, depart from me you workers of lawlessness.
Most witnesses understand this on a base level, imagining that their faith based on works, going out on the ministry is all that is required, and no depth of understanding is ever gained, that is speaking of my own experience when in a congregation. It is a shallow faith, one soon to be challenged. There is without doubt a veil covering the eyes of Jehovah's people and it will soon be lifted.
Love has no boundaries, it is up to each individual to cultivate love, and that love can be helped along, if we search for Jehovah as if looking for the most prized treasure, not a treasure that is here on earth, a heavenly treasure that our heavenly father rewards us with if we earnestly seek him, a love that when understood leads one not just away from doing wrong, a love than is inbuilt, inculcated within our every thought and action taken, the real works of faith, But, we must live by the words of truth, even if it means we lose everything, including our lives.
I chose to make a stand, and i have been relentlessly targeted by something demonic, Recently i have lost everything, stripped bare and i have been left a shell of a man, even my health has gone, because i will not compromise my love of God. And even now, after all my trials, i am still not sure my love is strong or my faith is enough, because who can know the heart, we can only hope in Jehovah and ask him to strengthen our faith, and also fill our heart with spirit to sustain our love for him, we cannot do it on our own.