As you bend, you SHOULD be pushing the strings together, and if you bend far enough, all three strings should be together under the fleshy part of your fingers. Definitely NOT “over the nail.” That sounds like a good way to lose fingernails and break strings.
What you SHOULD be doing is learning how to use the fleshy part of your right/picking hand (the part you use to mute strings to CHUG) to damp the strings you don’t want to ring (in this case the G and B strings). Ideally, you want to be damping ALL strings you don’t want to ring out, with part of one hand or the other. It’s hard to find a comfortable way to do this sometimes, but the more you get in the habit NOW, the better off you’ll be later – I don’t even think about it any more, in most cases (except where I failed to learn it in my formative years, and now it’s HARDER).
Good luck!