Heat after spay??

So I got my 7yo cat spayed recently (8/18) because she has a habit of going into heat very often, sometimes every other week. I've recently taken her from my parents house and saved up enough money to get the procedure done. She's still recovering, as in still wearing her cone and taking pain medicine until her stitches heal up completely, but last night (8/20) she went into heat. This is especially problematic because now she only wants to be around my 11 week kitten, who just wants to play, and now she'll let the kitten attack her sides and stomach without a care. This wasn't a problem until last night, and moving the kitten only upset my cat and she would chase me around as I carried the kitten to get to it. I live in a studio apartment and work full time so I can't keep them separated except to keep one in the bathroom so her stitches aren't attacked when I'm not home or asleep. I guess I'm asking if it's possible for her to even go into heat after a spay? Especially so soon? Or is this a temporary side effect? The research I did said it can happen if the vet did it wrong, but does that mean I'll need to save up for another procedure? Or should I go to another vet entirely? Any advise or info would be appreciated. I'm extremely frustrated by this whole ordeal and am planning on calling the vet after I get off work this afternoon, but I want to get others opinions first. Thank you.

Oh my goodness how frustrating and confusing!   A cat with no ovaries should, according to the text book, not show any heat signs, but occasionally they do.  There are some reasons for this: 1) An extra ovary tucked away somewhere, which happens (rarely).  In some extremely rare circumstances, some animals have two wombs but it would be incredibly unlikely to them both to be functional 2) ovarian tissue hidden elsewhere in the body, so even when the ovary is removed, the hormones continue to be made and do their thing. 3) The ovary being incompletely removed ie the vet left a little bit behind. I would also add number 4) because it has after all only been two days, that before the ovary was removed the early stages of heat started and haven't really had chance to settle down yet.  But it's not something I've heard of very much. If the uterus has been removed, then rest assured that your cat can't get pregnant (unless they have two uteri which I've never encountered). However it sounds as though you need to keep her in and calm as you can (having just had surgery) and contact your vet to make a plan of action going forward. Best of luck and please do let us know what happens!