Marvel owns her. She was in secret wars 2 first so they could keep the rights. Same with death's head who was in a one page comic in another comic before showing up in transformers. That's also why idw could not use her in their marvel follow up comic and just had spike get her powers without talking to much about her to avoid copyright. Again she would make a great iron man bad guy but you really need to update her look. The only thing is her human name Josie Beller may be in a loophole with hasbro. Marvel may have to rename her human name.
Idw had to cut her out of some of the reprint books along with Spider-Man, death's head and nick fury till marvel gave them the ok to reprint them.
Marvel did let them reprint the issues but at first they had to cut them out of the reprints! Hasbro has said on the transformers boards marvel owns her in the past when fans ask about her for comics and cartoons. Bring her back marvel!Though she was created for use in the pages of Transformers, her first appearance was a brief but major cameo in the pages of Secret Wars II #3. This was done specifically to enable Marvel to claim copyright ownership of the character. (A similar trick was used for the Marvel UK character "Death's Head.")
Because of this, Marvel owns the character of Circuit Breaker, though not the character's civilian identity of Josie Beller. This, in turn, has created a major problem for IDW, which now cannot reprint any of the Marvel Transformers Comics that star Circuit Breaker, which are issues #9, 22, 23, 46, 68, and 72 through 80, without permission. Earlier editions of the Classic Transformers trade paperbacks published in 2008 excluded these issues; in their places were brief synopses of those issues. However, later editions published in 2012 included the omitted stories. How long future editions will continue to include these comics remains to be seen.
https://transformers.fandom.com/wiki/Circuit_Breaker