Thank you for giving us more info. It is very good that they were able to leave the one ovary so that she isn't going through sudden menopause too.
My recommendations are aligned with Cathy's. I know that you are asking for poses (asana), but there practices she can do right now to comfort her and to aid with her recovery. As she heals and is ready for asana, we will have a better idea of what to recommend depending on how she is progressing.
Her breath is going to be her greatest tool for healing right now. Encourage her to rest one hand on her heart and the other on her belly and to take full, gentle breaths. Inhaling through the nose and the exhale can be through the nose or the mouth. For clients who are releasing (or wanting to release) trauma or emotion, I have them exhale through the mouth with a audible sigh. It may feel awkward or silly at first, but it is a wonder. I use this myself and it really is helpful for me when something comes up during my own practice that I want to let go of. She may need privacy to do this or someone, like you, close by just in case she needs you.
Another thing that I use for clients, and for my loved ones, is to oil and massage their feet. I use few different oils depending on the situation, Dr. Hauschka's Moore Lavendar Oil is wonderful for soothing and calming, but you can make your own too. I recommend organic, refined, untoasted sesame oil as your base. It will not have a smell to it, so you can add some lavender and rose oil, or another scent your sister enjoys. The oil choice is secondary to what the oiling and your touch will do for her. It is nurturing and grounding for her and will truly benefit her recovery and her wellness of mind.
The second chakra is the Svadhisthrana, which for women occurs between the uterus and the cervix. This disruption to the physical body may likely lead to a disruption to the subtle bodies. Ample rest and gentle movement, breathing with the heart and belly connection, and the oil-massage will all be of great benefit to your sister at this stage in her recovery.