While making choices for Liliana's last ability, if a permanent has more than one permanent type, it can count for any of them. For example, you could choose an artifact creature as the artifact you're sparing, another creature as the creature, and an enchantment creature as the enchantment. Similarly, you could choose an enchantment creature as both the creature and the enchantment that you're sparing, even if you control another creature and/or another enchantment.