Is it permissible for the young woman to turn the suitor down if she had no feelings for him?

Yes, it is permissible for her to do so.

Should one obey his mother even if she was wrong?

Obeying one`s mother is an obligation in matters that are beneficial to her and so long as she didn't drive her children to commit an act of sin.

Is it permissible to listen to chants praising the Prophet if accompanied by musical instruments?

If singing, or chanting in praise of the Prophet was accompanied by a forbidden musical instrument, then it is forbidden.

In our region in southern Oman, specifically in the city of Taqah, there is a mosque that they say was built hundreds of years ago. This mosque is surrounded by graves, meaning it is in the middle and the graves are around it. People in our area differ, with some considering it permissible and others considering it forbidden to pray there. Moreover, my grandmother saw in a dream that she entered this mosque..."