Why did my cousin act this way?

Yesterday my husband and I revealed to my family that we're having a baby. Everyone was happy for us but my aunt, cousin and my cousins roommate were silent and got up and left without a word. A few minutes later my cousin posted that she had made a second twitter account that was private she could "vent about personal things" on and "desperately needs a therapist to vent to". I should clarify thay my aunt and cousin do not like me and we're not on speaking terms but still. I don't get why they got so upset? My cousin is single and doesn't even want kids so it doesn't make much sense.
Why did my cousin act this way?
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