I really like the idea of two middle names. And I almost used Lavender Pearl. But my hubby vetoed it. I wanted a name that meant mermaid. Example : Sereia Lander Pearl. lol!
I like
Lavender Mary
Lavender Molly
Lavender Grace
Lavender Noelle
I’m a Pinterest Junkie when it comes to finding cool unique names.
Tiarella is the scientific name for the Foamflower and mean Little Tiara
Araliya is the name of the Plumeria flower in Sri Lanka
Araluen is Aboriginal name for water lilies.
Rosaura is Golden Rose in Spanish.
Lunaria is the name of a type of flower
Laelia is Latin for Orchid
Lilaea is Greek for Lilac and name of a water nymph
That’s all I can think of atm. But I do like Lavender as a name. It did take me a minute to warm up to it, but it’s really nice and stands out. 
Also, Bluebell is Beautiful! Definitely checkout Pinterest for that cottage core vibe you like
Cottagecore Names:
Amaryllis (Bluebell Amaryllis 
)
Briallan
Magnolia
Opaline
Cloverbell
Celestia
Maevea
Prairie (Lavender Prairie)
Amaevea (invented name I found online)
Happy naming!