gotcha. that's not a real reason not to pin. the only reason that I ever entertain is when someone is in Japan or a similar country that bans needles. When that's the case, you really have to look for alternatives to pinning. As long as you live in a country that does not ban needles, you don't have a legitimate excuse to not use them.
Hiding this from your girlfriend is a poor idea. Here's why: You're new to this, but you won't be forever. You won't just do 1 cycle. If you stay with this girl for awhile, you're gonna have to tell her eventually, because you don't want her finding out on her own. (she will). It's like ripping off a band aid, lol. Just get it over with now and never have to deal with it again. If she's not ok with it, and you're determined to use them anyway, you need a new gf who is more understanding.