Guest in Texas: Until you asked, I hadn't even considered that original sheet music might exist. (It doesn't exist for a lot of old folk songs.) But lo and behold, WorldCat.org tells me that a copy of the sheet music resides at the library of Cambridge University, described thus:

I'LL BE ALL SMILES TO NIGHT : SONG
Words, M. J. Ludlow. Music, Geo. Powis.
London : Powis & Co., [1866]
First line: I'll deck my brow with flowers.

In those days, British copyrights typically weren't enforced in the US nor vice-versa, so it wouldn't surprise me that a song that originated in one country would be bootlegged in the the other, or that someone would claim a bogus copyright.

Some libraries will photocopy sheet music and mail it to you—maybe even email the images—for a fee.