Plus idk if bf was complicit in keeping the party secret and keeping me out of the bridal party. Now I do not even know if I can trust bf or will hurt me too.
(Italics my own)
Look at what you've written, @Livinthedream11 . You are absolutely 100% rock solid that you "should" have been in the bridal party. You talk like there's a conspiracy to exclude you from your rightful place at the top table, and that your best friend was complicit in keeping the hen party a secret.
This simply isn't true.
No one is "due" a place in the bridal party other than the bride. NO ONE. The bride can go solo. She can have 15 bridesmaids. She can arrive like The Virgin Mary on a donkey, but with jugglers and fire eaters if she wants. It's 100% down to what she feels like.
She certainly doesn't owe her sister's best friend a place.
Given how unbelievably over the top your reaction has been to not being a bridesmaid and not being invited to the hen party, I completely understand why they didn't tell you about it. You're the wannabe bridesmaid equivalent of a Bridezilla.
"I don't know if I can trust bf"
Listen to yourself. Your pregnant friend has done nothing wrong. She doesn't choose her sister's bridesmaids. If she even suggested you, she'd be overstepping because it isn't her wedding. It isn't your either.
Check in with A confirming you're looking forward to hosting the party at your mum's house, that you are on decorations and dessert, and you haven't heard from B and the SIL about the food but you trust they've got it all in hand.
That way, as @Nocameltoeleggingsplease and others have repeatedly said, A knows what's being done by you and what's not your responsibility.
Then get over all of B's wedding stuff and focus on celebrating your friend and her plans for her new baby.