How do I tell her we dont need her to host the baby shower?

So when my boyfriends step sister found out we were expecting she immediately offered to throw us a baby shower. (we hardly talk to her) I greatly appreciate it but her and I have never really talked before and suddenly she talks to me like we're best friends, she's already got 70% of it planned even though it's about 3 months out.

She lives 4.5 hours away from us and is going to make the trip up but is relying on us for a ride back. With gas prices shooting up like crazy we can't afford to do an 8 hour trip just to take her home. ( before prices went up we agreed because it was only fair if she was going to spend all this money on the baby shower that we could take her back)

With her being our host I don't want to leave her stranded 4.5 hours away from home, so I just planned on no longer having a baby shower because I don't know anyone else who would step up to host it. Before we had a chance to talk to her about it,

I expressed my concern with how much everything was going to cost us with my dad (we were hopefully going to get most of our necessities from the shower) and He went ahead and spoke with our family friend who very kindly offered to throw us a baby shower at her home. I would much rather have our family friend host it because of the costs but Bfs step sister still thinks she is hosting it. I truly don't want to sound like an asshole and just tell her we don't want her hosting anymore.. I just don't want her to spend so much money on gas getting up here, plus the baby shower costs and then us having to make that trip back to her home and spend $170+ on gas..

What can we say to her, in the nicest way possible, that we don't need her to host anymore? She is so excited about it.. 🥺