So very sorry to hear about your wife.
It must be very hard to have to deal with this yourself whilst also trying to help your daughter get through it as well.
Perhaps you can put an album of photos together with her and perhaps a memory box or jar too. The box idea is that you put in it any items that remind you of your wife or have some special memories attached to them. The memory jar is an idea for you allow you to dip into whenever one of you is missing her. You write down any memories of her that you have on bits of paper or characteristics you remember about her, so that when you are missing her, you can draw one out at random and relive that memory, which although it may make you cry, may also make you smile.
It helped me to have flowers in the room to remind me that there were still beautiful things in the world worth living for and to give me a little hope for the future.
Talk about your wife with your daughter as often and as openly as you can. That will help. It's no good bottling things up.
We will be here for as long as you need us. Sending strength and hope.