Sana said muslims can only marry muslims because its written in the quran. Is that true?
Yes and no
It is allowed for men to marry to someone who isn’t muslim (if she is Christian
or Jewish, but it is not allowed for him to marry a non-Muslim woman who
follows any religion other than these two) while it is not allowed for women to marry a man who isn’t muslim
The justification for this rule was two-fold: 1) Technically, children
are given the religion of their father, and so legally speaking, the
offspring of a union between a Muslim male and a non-muslim would still
be Muslim; 2)It was argued that Muslim men are Islamically prohibited
from forcing their wives to become Muslim. Religious coercion is
prohibited in Islam. However, in Christianity and Judaism a similar
prohibition against coercion does not exist. According to their own
religious law, Muslim jurists argued, Christian men may force their
Muslim wives to convert to their (the husbands’) religion. Put
differently, it was argued, Islam recognizes Christianity and Judaism
valid religions, but Judaism and Christianity do not recognize the
validity of Islam as a religion. Since it was assumed that the man is
the stronger party in a marriage, it was argued that Christian and
Jewish men will be able to compel their Muslim wives to abandon Islam.
(If a Muslim man would do the same, he would be violating Islamic law
and committing a grave sin).
I hope that answered your question