After Caroline left the Mikaelsons and Hailey all did many different witch tests to make sure that isabelle was infact Klaus daughter.
They never knew the logistics of how she came to be, but they had other things to worry about such as Dahlia. Things happened they defeat Dahlia, people angry and so on. Isabelle was continued to be watched and loved in the compound. Many things happened within that course of a year, and Isabelle was threatened many times, but always kept safe by the mikaelsons. After Dahlia was killed not soon after back in Mystic Falls, caroline had turned on her humanity, but was unstable and waited bit longer. When Caroline was finally ready to take Isabelle back she found out that she was pregnant with the Jo and Alarics twins, that were magically implanted in her. So she decided to call Klaus and talk to him about the situation.
Kalus ended up keeping Isabelle longer. In febuary the twins were born, and a month later Marcel puts Klaus on trial with his sires; he bites Kol and Elijah and they suffer from his venom. Rebekah is undaggered and continues to lose herself to the Insanity Curse. Freya is poisoned. In order to save his siblings, Klaus has Freya perform the Life-Force Linked Chambre de Chasse spell to link them all to him; Freya combined Esther's Original Linking Spell and Dahlia's Immortality Slumber Spell to prevent them from dying. Klaus is daggered with and sealed away underneath .
Haley takes hope to a safe house that's protected with a spell, and she will start the search for a cure. Before she does that she meets up with Caroline where she gives one year old Isabelle to Caroline.
While that one year with mikaelsons Isabelle was loved.
The next to chapters are speed throughs of season 7 and season 8. It is not necessary but gives minimal information on what is happening in timeline, along with Isabelles family.