So sorry to hear about Sophie.
My male Korr has lost 2 bond mates. Sophie was about 2.5 years ago and Penelope last May. He seemed to do ok after Sophie died, but that may have been because Penelope was in the house (they were not bonded yet) and he could go visit her when he was out. I ended up having to bond him and Penelope a few weeks later as I got Sean. When Penelope died, Korr was depressed. He was kinda mopey and didn't eat as much for about 2 weeks. He would run around when out of the cage, but he just wasn't himself. I pretty much had to make sure he was eating, so I gave him some alfalfa pellets (I have some for my angoras) as he likes them. He also get some extra treats and veggies. He did get back to his normal self, but really perked up when I brought Amelia home.
You really need to make sure she is eating and drinking. Beyond that, try some new toys of getting her out of the cage more often. I would not get another rabbit yet, it would be better to wait a little while until you and her are ready.