I'm getting a newer feeling on this one - this is the sort of thing that were I holding it, I'd have a much better idea.
It looks like cotton seersucker, which was popular in the early to mid '70s. There are so many florals over the years and a lot in the '70s so unless it has a reference point, I wouldn't call it a Liberty print, but you could call it a Liberty-style or a Laura Ashley-style or a traditional floral, it has a Victorian look I think. I agree with Barbara in that the ribbon treatment was used in the '20s but it's easy enough to make at other times.
The questions that would help are: what material are the buttons made of? Is it stitched with a cotton or a polyester thread? Is the decorative trim synthetic? How are the seams and hem sewn? I'd also look at the belt loops - it looks like a nightgown but the belt loops and the sash suggest it is a Victorian style made in more modern times as a dress.
On the available information, I think it's a '70s dress or a costume reproduction.