New Great Dane 11/m need to introduced to the 7/y cat

Question
I have adopted a Great Dane, 3 days ago. She is 11 months old spayed dog. We tried to introduce her to my 7 year-old cat and followed "by the book". Let them sniff each other first, while holding her, they seamed relatively ok. However few hours later she came up to the cat alone and tried too sniff him. He attacked her and scratched her face. Then he ran but she caught him by the head and would not let go. We separated them immediately. The dog is fine now, but the cat would not come out of the closet since then. I tried to play with him and gave him his food and toilet in full access near the closet.
What Shell I do now? I can't keep them separated forever.  Please advise?

Answer
Yevgeniya,
Because the puppy has already attacked the cat you are going to have to keep them separated unless you are watching them. Because the experience started out bad for the cat, he is not going to make it easier for her to get used to him. What you  need to do is keep her on a leash so that you can correct her when you see that she is starting to be rough with the cat. What I would do is teach her a "leave it", so that you know you can stop her from touching the cat. Until both of them future out that neither is leaving, they will continue to have issues. When you are not able to watch them, even for a second, make sure you put her in her crate or other area that you have designated as her spot. I hope this helps. Sorry that I just got back to you now...