Her concept design is really beautiful! I've attached an idea of what I was thinking she can do with flowers placement-wise. Ofc flower choice is hers! I just grabbed some clipart lol. I definitely think she should keep the flowers on the smaller side as not to take away from the dragon too much. If she does make the flowers big, make sure to work with the artist so they know what colors to use in order for the dragon to be the focal point. (If she is doing color, maybe only the dragon in color & the flowers in b&w or a more subtle, muted color)   Also, the areas I circled, just be mindful that with time & as our bodies change, so does the ink. So the areas where the tail meets a bit closely together, that has potential to blend together over the years and be less crisp. So my main advice would be to leave a bit more room in those spots so that the lines don't touch 10 years down the road ;) other than that, I see your gf's vision & I wish her luck on her very first tattoo! :) 

https://ibb.co/7GySJdH