LLMs don't really retain the full data anyway and it "should" be scrapped once the training is done. So yes, technically you might be able to demand that your data is to be removed from the training data, but that's going to be fairly hard to prove that it exists within the model.

As far as I see, GDPR would not applicable here - GDPR is about control of "your data" as in "personal data about you as a private individual"[1], it is not about "your data" as in "content created or owned by you".

[1] GDPR Art 4.1 "‘personal data’ means any information relating to an identified or identifiable natural person (‘data subject’); an identifiable natural person is one who can be identified, directly or indirectly, in particular by reference to an identifier such as a name, an identification number, location data, an online identifier or to one or more factors specific to the physical, physiological, genetic, mental, economic, cultural or social identity of that natural person;"