It seems that if a person is half of one and half of the other, in their younger years they try may be more a whole of one than Thou, while seeming to reject the other half of their heritage. Leonard Nimoy, playing Spock, did this with finesse through TOS and the ST movies. We learned his Human side wasn't dead and was a great resource.
Sela? I would say good idea/bad execution. I could see Half Human/Half Romulan on the Fed side of the Neutral Zone being a fanatical Fed, but, having to make peace with their supressed inner Romulan. There is no plot opening for Sela to do this.
A more interesting take was "The Drumhead". This struck me as the most realistic. Simon Tarses has Romulan ancestry and wants to hide it. Tarses is ambivalent as well. It raises a whole slew of questions of the enlightenment and tolerance of the Federation. One of their citizens felt the need to lie on a Star fleet application.
In real life I've seen Americans of Arab descent be simultaneously appalled at Islamic terrorism and their medieval societies and at the same time be appalled at flippant jokes against Arab culture. They seem to be American as all get out and most are Christian.