Who should be invited (Baby Shower)?

If the shower is being held at your aunt's home, space will be a factor. You'll have to make some tough choices, but your best bet is to include your closest family members (the aunt you exchange Christmas cards with but otherwise don't really see won't be offended to not receive an invite. The cousin you get together with every few weeks will) As for your friends, the 5 girls that you want to "cement friendships" with can probably be excluded. Your baby shower isn't really the venue for that, and if they don't know anyone but you and each other, they'd probably just end up forming their own little group.