My nani’s family is ismaeli
We avoid eating their food but sometimes we failed and they forced us to eat what my anty cooked. She believes on Allah swt and Rassoul e Khuda and Imam Ali (as). Sometimes she does namaz and fast

Is it okay to eat her food when we have no choice?

She is considered as Muslim right?

If she believes in 3 basics and Fundaments of Islam i.e. Oneness of Allah, all Prophets sent by Allah and Prophet Muhammad (pbuh) is the last Prophet of Allah and The Day of Judgment (Qiyamat) then she will be considered as Muslim and Tahir