JarJar, I like! Only tweak I’d suggest:

“Because he no longer needed you. After his return, and your escape, he saw his creations as a threat
to his power. Your blood… is his blood. You… are a Palpatine.”

“The only reason for your existence was to be one of his vessels."

The only reasoning is to not downright say she is a clone, but she was created from him. This leaves things a little more vague which I think might be a good thing in this situation and help smooth out “Rey Palpatine” better. She’s not a grandchild, and it’s not explicitly stated that she is a clone, but that she was created from him.

Plus it can help make Luke’s “…some things are stronger than blood.” hit a little bit harder.