Again, purely a matter of taste. The bluegrass audience decides what bluegrass is, and it has decided emphatically in favor Rhonda Vincent. It doesn't follow that you have to like what she's doing if you're disinclined to do so.

I'm not sure, however, that calling Vincent's singing "country" amounts to more than an observation. It certainly isn't a criticism, since bluegrass owes a great deal to country music, and not just in repertoire. Bluegrass began decades ago as a form of commercial country music, and country vocalists have influenced bluegrass singing, and sometimes vice versa. Bluegrass was certainly influenced by the Appalachian stringband tradition, but it is not itself a form of traditional music.

I suspect that you're coming to bluegrass commentary from a position outside the genre, as opposed to that of someone immersed in the music. Your right, of course. But I do think that as a consequence you're missing the nuances and complexities, both historic and current, of the genre. In this instance it's the tangled relationship between bluegrass and mainstream country music. To your statement that Vincent sounds country, the response has to be, "Well, of course she does." It isn't "Gillian Welch," who has more in common with early Bob Dylan than with Bill Monroe.