I think
Poppy is really sweet for a little girl and could even work for a teenager, but I just can't seen it in an adult. Then again there are a lot of names that are popular for babies now that I can't imagine on an adult. I guess by the time all those babies are adults I will be used to the names.
Anyway I think
Poppy would be a great nn or pet name. By that I mean a pet name for a child not an animal :) You know, a term of affection not derived from the childs actually name. The only name I think of off the top of my had that you could use
Poppy as a nn for is
Penelope.
I like that you have chosen traditional mns with
Poppy. I like
Poppy Eleanor and
Poppy Madeleine. I think I would avoid
Lilian because it contains the word
Lily and
Poppy Lily is just too many flowers.
I think
Milo,
Jasper and
Felix all go really well with
Poppy. The girls names seem a little too traditional.
Ruby is probably most similar in style but I don't like that they both end with Y. I like
Poppy and
Eleanor best I think. But you know little
Eleanor might wish her name was more fun and cute like sister
Poppy, and a grown-up
Poppy might wish for a more serious, dignified name like sister
Eleanor.