"You're funny Doctor.." Heart rolls her tongue, lapping that blood that Seira drew from her with a bite. The wound on her tongue heals without too much issue, but it only prompts Heart to act more out of line.
She knows all of Seira's soft spots, all because of Skadi before her. And while she didn't intend to abuse them, the Doctor's stubborn will prompts that specific push.
Those fingers nudge up inside, her hand releases their neck to play with her body. All while she returns to that kiss, returning the bite on Seira's lip much to the other's defiance.
The longer she's near, the harder it'll be not to feel good. As the body rejects everything but the cells decide they enjoy Heart's touch.