The most important part of Christmas is the Mass. Let that be your celebration. If you know someone who is also going to be alone, it is possible to invite them to join you for dinner. Or maybe you could visit a nursing home. Most people in nursing homes get one visit a year from their families. Many never see anyone, especially at the holidays.
Also, consider visiting a hospital and get permission to visit some children or others who are sick. My sister just got out of the hospital yesterday, but we thought she might not get to come home in time. She is still very ill, but being in the hospital would have made her feel even worse.
We are not having a dinner or anything today or tomorrow since she can’t eat. Our Christmas is the gift of her continued life and presence in our lives. Make sure you understand what you might be missing this Christmas. Dinners and gifts are nice, but not essential. The welfare of loved ones and bringing joy to others is much more important. Of course the most important thing is the Birth of our Lord. Remember Him and be at Peace.