My friend reverted to Islam few months back and this is her first ramadhaan. She is from Russia and their fasting hours crosses 19 hours a day. She kept her first fast and was in very bad condition due to womiting and bad health. She was even referred to a doctor who advices her to take plenty of liquid. I would like to ask you is it compulsory for her to keep fast? I am afraid that she might convert back by looking at difficulties. Although she herself is ready to do any kind of sacrifice. Kindly let me know what to tell her.
In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
We commend you for your concern and support for your friend. Reverts to Islam need our support and counsel. This is a great act of virtue. Continue providing your friend support and comfort. Inshallah, she will become a practicing Muslimah, which will be in your eternal account of good deeds.
If your friend is sick to the extent explained in the query, she is exempt from fasting. If she broke her fast due to her not feeling well, she would have to make Qadha (make up) for the missed fasts after Ramadan. If she is getting sick due to the fast itself and the fasts are long, advise her on Sehri and the type of nutritious foods she should take at Sehri to maintain her health and energy.
And Allah Ta’āla Knows Best
Mufti Arshad Ali
Darul Iftaa, Jaamia Madinatul Uloom (Trinidad)
 الدر المختار وحاشية ابن عابدين (رد المحتار) (2/ 422)
(قَوْلُهُ خَافَ الزِّيَادَةَ) أَوْ إبْطَاءَ الْبُرْءِ أَوْ فَسَادَ عُضْوٍ بِحَرٍّ أَوْ وَجَعَ الْعَيْنِ أَوْ جِرَاحَةً أَوْ صُدَاعًا أَوْ غَيْرَهُ، وَمِثْلُهُ مَا إذَا كَانَ يُمَرِّضُ الْمَرْضَى قُهُسْتَانِيٌ ط أَيْ بِأَنْ يَعُولَهُمْ وَيَلْزَمَ مِنْ صَوْمِهِ ضَيَاعُهُمْ وَهَلَاكُهُمْ لِضَعْفِهِ عَنْ الْقِيَامِ بِهِمْ إذَا صَامَ (قَوْلُهُ وَصَحِيحٍ خَافَ الْمَرَضَ) أَيْ بِغَلَبَةِ الظَّنِّ كَمَا يَأْتِي، فَمَا فِي شَرْحِ الْمَجْمَعِ مِنْ أَنَّهُ لَا يُفْطِرُ مَحْمُولٌ عَلَى أَنَّ الْمُرَادَ بِالْخَوْفِ مُجَرَّدُ الْوَهْمِ كَمَا فِي الْبَحْرِ وَالشُّرُنْبَلاليّ
This answer was collected from Fatwa-tt.com, which is operated by the Darul Iftaa of Jaamia Madinatul Uloom (Trinidad and Tobago) under the advice and guidance of Mufti Ebrahim Desai (Daamat Barakaatuhum) of South Africa.