HELP! Telling my daughter about the new baby

Okay beautiful Mommy’s I need help or some advise. My daughter is 6 and she is very much a mommy’s girl who gets jealous very easily. My boyfriend and I found out we are expecting our first child together due in August, we are over the moon excited but I’m still stuck on how I should tell my daughter. She’s not overly happy with having to know share things with my boyfriends son who we only have every other weekend.

Sorry for the long read.

Any advice would be greatly appreciated, thank you!