Okay, some things I noticed in the video.  The main things.

The hand and her are unrelated, I believe, because look at that surprised eye.  Just before Green Thing skitters off.  Also there are singe marks on the sides of the cave and clear damage.

Another thing I noticed.  There are remnants of his mansions wallpaper and floor in the cave.  Peeling off.

There’s glowing marks from here too.  If you look closely, you’ll see the checkered tiling.  More remnants.

She checks to see if Mystery’s trail is there, but the flower dies, signifying nothing.

She catches Lewis’s scent.

It forms a flower.

She blows the petals and they land on Lewis’s locket.  That’s how she tracks.

She checks to see the traces of who she can get.  She gets the three humans.  She cuts them off because she’s not after THEM.

She uses Lewis’s locket to somehow get a bead on Mystery.

He’s mad and her hand is on fire.  His locket blows her arm off.

Lewis can summon objects.  Those lamps appear.  Also Shiromori’s weapon appears to be scissors.  She’s a gardener.

The giant flowers starts shrinking as she loses Mystery’s “scent”.  So she blows the petals and follows, she didn’t have time to fight the angry pink skeleton man.

Canon pepper sisters.  Arthur can’t handle spicy food.  Lewis’s image starts blanking out and Vivi’s eyes change the same pink.  

She finds him.  Either this is symbolic.   Or she’s actually there.  My guess is the former.  It looks like he didn’t know she was onto him.

He put the flower petals in his locket and it healed the crack.  I believe the locket turning blue didn’t have to do with Vivi.  It’s a different color, it’s grayer.  I personally headcanon it turned blueish gray to signify a broken heart.

Because it turns gold again when he adds her petals.  So his heart is healed with new purpose.

Was he drinking coffee?  Why is there a coffee cup and table with one chair.  Lewis is lonely.

He made a table and coffee cup, because it disappears in a puff of pink fire.  Also the dead beats seem to have their own personalities.  They’re all making different faces.

Chicken in an egg under hat?

Pepper ornaments.  That is all.