Is the Prayer Valid If You Don’t Recite the Tashahhud?
Reciting the tashahhud is necessary (wajib), both in the first sitting (after two rakats) and in the final sitting (at the end of the prayer)–but not obligatory (fard). Omitting it doesn’t invalidate the prayer, but does make it deficient.
When a necessary (wajib) action is left forgetfully, forgetfulness prostrations are necessary–but not when a necessary action is left deliberately. [Shurunbulali, Maraqi al-Falah; Ala’ al-Din Abidin, al-Hadiyya al-`Ala’iyya]
In your friend’s case, she needs to:
 Take the immediate, reasonable means of memorizing the tashahhud;
 Sit for the extent of the tashahhud, repeating some invocations (such as Subhan Allah, Alhamdulillah, La ilaha illa’l Llah, wa’l Llahu Akbar).
No forgetfulness prostrations are required, nor does she have to make up or repeat such prayers.
Answered By: Shaykh Rahil Mumtaz