This is going to be a rather unorthodox question by me, as I can't fully legitimize the claim about to be questioned, but today, in conversing with a colleague of mine, the Shelleys popped up in conversion. During this conversation I was told by them that much of Percy Shelley's work (or at least some of) was actually just claimed to be his work but was instead written or mostly influenced by Mary Shelley.
Now even though myself and my colleague are not literary scholars, nor even writers or English professionals, I still view most of the things they say as credible as that is what my experience has been with them when fact checking claims they've made before. However, with this most recent claim, I cannot find much. When digging around the only bit of controversy I've found is regarding the debunked claim that Percy was actually the true author of Frankenstein. Yet that kind of is the opposite of the claim made. Ultimately, I'd like to know if there is any evidence that gives weight to this claim, or if there was perhaps another influential romantic era couple of which this dynamic did exist.