I had my hysterectomy when I was 21.
For the first few days she will need ice, not heat. I advise getting high-waisted underwear at least one size too big (maybe two), to wear after surgery. There will be swelling. And get another pair or two that is a size or two larger than that. Wear both, and place an ice pack between them. For the first few days, ice and Advil are your friends.
If she has an abdominal incision, she will not be allowed to turn to the side to reach for things. This is incredibly inconvenient, because at home everything is on side tables. Get her a table that can go over her lap. Ideally one that stands on the floor and not on the bed/sofa.
She will need to raise her arms over her head and hold them there several times a day, and take short walks several times a day. Without functioning abdominal muscles to carry some of the load, walking is hard, exhausting even. Standing is hard. A plastic stool for the shower is very helpful. She may need your help in the shower as well.
Be present for all conversations with the doctors, she might not be able to remember them clearly, because she will be full of drugs. Take notes! Ask questions! You will be the one ensuring that some parts of the recovery plan are followed.
Other than that, get plenty of fluids and fiber into her. Bowel movements are painful and constipation is worse. She'll be in bed for a week or so, so get some new movies, games, books, activities, etc.
She'll get tired quickly, so keep an eye on her when she is socializing and make sure to step in if she needs to rest. Be prepared to entertain her visitors. During the first few days, they won't get more than an hour or so with her, if that. You might find yourself playing host to people waiting for her to wake up. Let her sleep, they can wait. When she is asleep she is healing and is not in pain.
But, you might need nibbles and a plan to handle guests. She will need small meals, eaten frequently. Bringing trays in and out is the perfect time to check and see if she wants a visitor.
Accept help! She will need your help to eat, move, pee, poo, shower, change clothes, fill Rxs, etc. You will also be the only one doing the regular chores, errands, and housework. Let people bring meals, wash dishes, run errands, clean, put away, and all that other stuff. Save yourself to help her shower and be a shoulder to cry on.
Also, the drugs are powerful. For the first few days she will be experiencing the lingering effects of anesthesia and powerful narcotic pain meds. Buy a book, an easy, fast read that isn't complicated or full of big words. If she is bored or having trouble falling asleep, read to her. She will be able to focus on your story and not her discomfort. That, and the drugs, should help her drop right off.
This surgery has a lot in common with a Cesarean section or an appendectomy or bowel cancer removal or other lower abdominal surgery. It doesn't have much in common with having endo. When she wakes, her endo will be gone and her pain and problems will be different. Chat with friends and relatives who have had abdominal surgeries to get an idea of how their recoveries went.
In fun, less practical, ideas. I wore these types of nightgowns in the hospital, with matching satin kimonos (the wide kimono sleeves leave plenty of room for the IV). The side slit accommodated my catheter tube without lifting the side of my dress. The strappy top doesn't interfere with IVs. They are easy to get on and off while seated. The are short enough that you do not need to remove them for a pelvic exam or wound care. They look very nice when you are sitting or lying in bed, with the blankets over your lap. They are classier and more comfortable than hospital gowns. And there is something about "getting dressed" every day that adds normalcy. Just wearing the hospital gown and changing it when it feels dirty made me feel like a sick person, an invalid. But, post-surgery I was a healthy person, and wanted to feel that. Bonus, I got lots of positive comments taking my fashionable, prescribed strolls around the ward.