Pregnant with #3, DD1 not happy

I'm currently pregnant with #3, and a few times have approached the idea with DD1 (3y 3m), but each time she has gotten really upset and told me that she doesn't want another baby round here.
After DD2, I stayed in hospital for a lot longer than expected, and due to a few things, she didn't see me for 5 or so days (where before she had been with me constantly - the night I was in labour was her first away from me). I'm worried that she thinks I'm going to disappear for a long time again and wont come around to the idea. Breaks my heart seeing her so upset about it.

I know I've got lots of time to prepare her for this but hoping to hear others experience, or any advice to prepare her over the next 7 months