Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, we would like to thank you for the great confidence you place in us, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.
The Prophet (peace be upon him) is reported to have said: “Islam is built on five pillars; to testify that there is no object worthy of worship or devotion) except Allah; to pray; to fast in Ramadan; to give charity; and to perform the pilgrimage of Hajj if one is able to do so.” (Al-Bukhari)
Answering your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic Scholar at the Islamic Institute of Toronto, Ontario, Canada, states,
It all depends on why she does not pray or fast. Thus, if she does not pray or fast out of laziness without denying their obligation, then she is still considered a Muslim – as stated in the `Aqidah Tahawaiyyah; a person guilty of major sins does not go out of the fold of Islam unless he or she justifies them or declaring them as lawful.
Having said this, let us not forget that Prayer is the most important pillar of Islam: It is the means of salvation and the key to paradise. So, by neglecting it, one is endangering his or her salvation.
Allah Almighty knows best.