The mother is being unreasonable. On the other hand I fully understand her; 19 is young. Too young these days in the Western world. But asking a young couple to wait for 1,5 years is slightly risky. If I were a mother I would never encourage my children to date - especially after they are in love and comfortable enough to marry each other. Adoonyo laga daba cararaayo one is unintentionally opening the door to zina and temptation.
So my advice? Keep working, time flies, dec '13 will be here soon enough iA.