Difficult situation

My cousin sister have been trying for baby for past 5 years and she couldn't conceive. Also when she went for her medical check up the doctor said its difficult for her to conceive because of her ovaries, overweight, irregular menses and some other complications. Her in laws have been pin pointing she havent got pregnant yet and she used to call and msg me that she is under depression and she cries almost every night for a baby. ? I'm now 3 months pregnant and I've not officially announced to others accept my immediate family. Should I personally message and tell her before I announce it or just let her know through social media? Ps: She is 3 years older than me and I just got married in January end. We are the only grandchildren in the family too. I dont want her to get hurt or get more stress. Also my baby will be the first great grand child. How can I let her know?