If God is a God of love and God experiences love and relationship within the Trinity, and love is a willful act, then can one of the persons of the Trinity choose to stop loving another person of the Trinity?

This falls into the realm of philosophical theology- of trying to figure out who God is outside the boundaries of Scripture. Philosophical theology has some uses, in that it might give you some Implications of the truths found in Scripture, and certainly the truth we find in Scripture is that God is a triune God. He is one God in three persons - three persons, one God. But that question - since God is love, is it possible for one member of the Trinity to not love another - the question answers itself - God is love; therefore that's not possible.

The bigger issue here is that trying to pick apart who God is - to maybe find chinks in the armor, so to speak - it's dangerous on two levels. The first level, first of all, this is the question of someone who's trying to figure out if they can find a weakness in God. They're never going to be able to do that, and it's dangerous spiritually because we're dependent on God alone for eternal salvation So there can't be a weakness in God.

The second danger is that this incurs the wrath of God. We are called as humanity to be worshippers of God, not those who try to philosophically pick him apart and denigrate him. This never goes well, and this is the sign of an unbeliever. Instead unbelievers are called to repent of their sin - the sin of denigrating God, of seeing him as less than holy, less than righteous, less than perfect, and fall down and worship him, asking for forgiveness, repenting of sin, and being those that now see this glorious triune God as the God worthy of worship. That's the bigger issue. So it's better to stop asking those questions and simply look to Scripture to see what Scripture says about our glorious God.