Don't panic. It IS something you need to talk and think about carefully, but it's not necessarily creepy...
I think you definitely need to talk to your daughter about this. I'd suggest you ask her straight but gentle questions if you can. If you can manage to be calm, you could be very direct and say "I'm worried you may be getting to old to share a bed with your dad. How do you feel about it?"
If you get any sign she is uncomfortable about it, then you need to take action to stop it. If she seems happy, then you can have a conversation about how it will need to stop soon, because it isn't appropriate for a man to sleep with his daughter when she becomes a woman.
And is it possible for you to talk to her dad? I know (from personal experience) how hard it is to talk to exes. But if you can, it will help you get an idea of what he feels about it. It might be that he wants it to stop, but doesn't know how to do it.
It is one of those situations/family habits that can just evolve. It starts naturally, and then you have to work out how to stop it...
I still share a bed with my 12yo son quite often - maybe 3 nights a week. It used to be much more - almost every night. I was totally happy and comfortable with this until he started high school, then I started to think "Hmmm, maybe he's getting a bit old". I decided it was time he slept in his own bed. I talked to him about it, and because we have a very open trusting relationship, I was able to be pretty direct with him. I said that he was at an age where he would probably be getting sexual feelings quite soon, and that he might wake up with erections, and that it would not feel right r comfortable for either of us if that happened when he was in bed with his mum! He took the point, and immediately started sleeping in his own bed.
However, it was only a month or so before he started coming back into my bed. The first time, he was ill and needed comfort. Then there were a couple of evenings when we were watching a film together and one or other of us just fell asleep. We both like it, and we often go to bed at the same time, so it's easy to let it happen. It's cosy and it absolutely isn't sexual, but I am now hyper-aware that he won't be a child for much longer... So though he is still entirely comfortable with it, I no longer am. I will be sad to lose the cuddles, but I think it needs to end.
Incidentally, I think this is one of those areas where it is trickier for single parents than couples. If you were still with your DD's dad, or I was still with my DS's dad, and our 12 yos were climbing into bed with both parents and sometimes sleeping there, no-one would think it was creepy, just squashed!