It depends on the betta, and what kind of tetras they are. Neons seem to be generally ignored by bettas, but some of the more rounded, larger tetras... not so much. Of course this also depends on how much space you have in the tank. Doing a school of neons in a 10 gallon with a betta is risky to begin with, but if the betta is ignoring the ones you already have, I don't see why completing their school would change that. Just make sure you do remove the glolights first, to avoid overstocking.
