From the sound of it, your best bet would probably be to add some code to your widget that checks the incoming HTTP Referer header and if it indicates the request is coming from the parent site just drop the GA event altogether. Alternatively, you could configure your GA4 settings to filter out any such events. If neither of these solution suits your needs, there may be more advanced methods of intercepting these requests using service workers, but that would likely involve implementing more complex functionality to check whether each fetch is relevant before deciding whether to let it through to GA4.