My mom came to U.S last year by herself, she did not know any word of english except 'Thank u'. I wrote a letter with my sevis #, address and phone number, flight schedules and request to any officer who may inquire her, to help her if she gets loss or confuse.She carried that letter all the way. She told me many people helped her finding the right plane, and also she met  few nepalese on the way.She was very excited by adventure to come america by herself..So dont worry much, your mom will travel fine.,Try to get her route thru' Bangkok,so she will meet many nepalese there, who will definitely help her.