You really do need to be on your mettle, that's for sure. While the questions or claims are usually not theologically deep (quite the contrary), the people asking them are generally persistent and convinced that they are right in a way that seems almost pathological to the average Christian, and can easily lead to intimidation.
Since she brings up Ramadan as an example of the scripture that Islam has supposedly preserved, please see the video below for some facts regarding how well that goes. It's from a Protestant Christian, but all of my Egyptian and Sudanese friends (and also those who previously lived in Kuwait, Saudi, and other parts of the Middle East) from church tell me that the observations that this man has made are borne out in reality in Islamic countries, re: Muslims eating
more during their fasting month, not being productive (since society essentially shuts down during the daylight hours), being wasteful, etc.
Ramadan is fasting in the same way that jihad is just an inner spiritual struggle, or the jizya is just a small additional tax levied to compensate for non-Muslims' not giving zakat.
By all means, be courteous to this woman or any other Muslim you may correspond with, but do not lose sight of the fact that all replies you may get will be tailored in such a way as to make Islam look superior to Christianity, in so far as it is possible (they would love for everyone to join their cult, obviously). She would not, I imagine, put up the Muslim fast practices as an example of a way that they have preserved what Christians have not if the comparison were instead between the Islamic Ramadan and the EO fasts or the Coptic Orthodox fasts, since we both fast to a far greater degree than Muslims do -- and they're
actual fasts, too, none of this "I gave up candy bars for Lent" stuff.
So Islam is more stringent than Western creampuff Christianity. So what? It's still false and from Satan.