I am going to start with my standard answer to such questions: “What did the doctor say?” Or in this case the ophthalmologist who did the cataract surgery. Only she knows what was done during the surgery and only she can wisely recommend a recovery period and what to avoid during that period.
In my own case, in my mid-60s, I had both eyes done: I felt fine within a couple of days. I still did some Yin Yoga, but I avoided any inversions or any position that would put my head below my heart. I was told to avoid anything aerobic for a while, and to avoid lifting any heavy objects (nothing over 5 kilograms or so). No hot tubs, no swimming, no dunking my head under water. It was after my one-week check-up with the ophthalmologist that he told me I could pretty much go about my normal yoga routine, but he wasn’t suggesting I do any contact sports.
For other people, they may be told to avoid strenuous activity for up to 2 months! Everybody is different. Thus, the importance of your student asking her doctor, not you, what is okay to do and what to avoid.
If your student did not ask her doctor for any advice, suggest she do so as soon as possible. But, in the meantime, don’t let her lower her head. Avoid any strenuous activities until she is given the all clear. No aerobic vinyasas, no breath retention or harsh pranayamas.
Everyone is different: there is no one prescription even for simple procedures like cataract surgery that will work for every body. What will work for your student? I don’t know. Neither do you. Ask the pro