As soon as 'his' head was out of the watter, Kevin grabbed Gisela, forcing another kiss on her. The natural mermaid tried to end it, but without success.
Kevin was now maintaining Gisela under watter, just like she did seconds before. But unlike Gisela, Kevin was just a slave of his newly formed mermaid's instincts. For 'him', Gisela was a potential rival, a stranger that wanted what she considered her territory. She needed to defend it, to make it clear to that stranger than living in that sector mean submitting her will to Kevin's one.
Gisela finally accepted that she was overpowered, acknowledging she just got overthrown. From this instant, she will forever obey and protect her new matriarch, a matriarch she herself created.
The mind of said matriarch too, was altered. Of Kevin, only his memory survived. The siren that now existed in his stead having few things in common with the human she used to be. She sensed Gisela used to be a matriarch herself, a powerful one even, making the former-human the head of a lot other mermaids, their mind now submitting to hers instead of Gisela's.
Wanting to know why she become the wonderful being she now was, not-Kevin-anymore asked "Why did you bring me here, daughter? Why have you changed me?"
"I sensed another mermaid on you, Kevin, ma'am. I wanted to use her boyfriend, you, to force her in our shoal." Dutifully answered Gisela. "No offence Kevin, ma'am."
Kevin then sniffed herself. "I sense her too." She said, before getting out of the bathtub. Being a former human, she was able to change her tail in legs without any accessory. "How I wish having legs again was the only thing I needed to make that whore one of us…" Then, after drying herself, she changed back to her old self. Physically, at least. "But it will be easier as her lover."
The siren then spoke directly to Gisela. "You should use that necklace of yours and go back to your human guise, daughter. After all, I feel the honor of making my ex-girlfriend one of our sisters should be yours." After dressing, she added. "And please, when I don't need to use that dreadful male form, call me Kendra. But for the time being, we should act as lovers."
"Of course, my love." She responded, acting like she truly was romantically interested in her disguised matriarch.
When Gisela was finally dressed, the two exited the hotel, arms in arms, Gisela tenderly hugging the disguised Kendra, her head resting on her fake-lover's shoulder.