"Leah crushed her mouth with a kiss, searing and hot. Allison clung to her, suddenly unable to stand on her own, pinned between Leah's hand and lips. She accepted Leah's tongue, which touched her own, retreated, and then sought her again. Leah's tongue was so much softer than the rest of her."
Allison just wanted to try something, maybe find a sort of substitute for what she's already got. Leah's more than happy to give it to her.