Whatever you do don't change your plans and stay excited. Your Mum is an adult. She will cope and will find her own path and routine when you are gone. She will be so proud of you going off and finding your way, setting up a semi independent life. The household will be very quiet but people are far more resilient than you will ever know and she will adapt to the new normal. Enjoy your time and look forward to the time you can come home again and catch up with all your exciting news.