I voted for Mabel because Hazel and Juniper sound a little strange to me as siblings, but I just had to tell you that as a combination I think Hazel Rose is completely gorgeous! So pretty.
I prefer Hazel, and if you go with that you get the whole bushes/trees association. But you'd have to be sure that that's something you want. Linden and Finley sound more like boys' names to me.
Maybe a combo since Finley and Linden are somewhat boys names (though I like both) and consider Lindley? Maybe I'm making that up but I feel like I've heard it as a name before!
Re: Baby Sister For Juniper
I really really like Juniper, btw. It's awesome.
Not everyone can breastfeed - Mammary Hypoplasia/Insufficient Glandular Tissue Awareness
Linden and Finley are both masculine and not appropriate for a girl. Save them for a boy.
MC June 2015
MC January 2016
Compound Hetero MTHFR Gene Mutation
Hazel is nice, but too themey with Juniper.
Linden or Finley are just no where near as good as Juniper.