In wa-in taku, in is a conditional particle and taku is a jussive form of the defective verb kāna, yakūnu. The expected form takun loses its final nūn, a recognized shortening in classical Arabic.
The following clause, qad sāʾatki minnī khalīqatun, develops the condition: some habit or trait of the speaker may have displeased her. Khalīqah points to a characteristic of character or temperament.
In the pattern in ... fa-sullī, the response is expressed through an imperative. The condition and its response should be read together, not translated as isolated fragments.