how to keep the cone, on?

hi all, my girl got surgery to get spayed about 6 days ago, they ended up ripping open yesterday so we had to get her restitched yesterday morning and are very on top of her wearing her inflatable donut. however, she keeps slipping out of it, it’s attached to her collar and we’ve tightened it this morning cause she slipped out of it last night. we have a regular cone but fear the same issue if we use it cause her head isn’t much bigger than her neck. any tips would be greatly appreciated.

feat. charlii in donut jail for the next 9 days 🍩