Women like muscles, but not steroids. From my experiences they like a little muscle, but not a huge bodybuilder type build.
Also they hate guys who are obsessed with their body, so if you are into the bodybuilding thing just keep it to yourself and act like you just workout a few days a week for fun. They can't stand guys who are into their body and typically see it as a turn off. Just act natural and consider it a non issue, don't get all crazy with her about your "supplements" and "diet", they don't want to hear it. Act like you don't care and just lift weights casually.
^^^This is my go-to tip on how I've met every girlfriend I've ever had, and my wife.
My wife and I started dating when I was at my biggest playing football. I looked like a full-on offseason bodybuilder, which I was at the time as well. She asked me if I was "into bodybuilding and that kind of stuff".
I said: "no, I just do some push-ups and sit-ups in my room to stay in shape. And you know what, football practice is really tough and wearing those pads all day and running, I think, really changes the way your body looks." I had strategically hidden my Dorian Yates 1993 black socks poster, and my Flex magazine collection, and my Masteron amps, under my bed in my dorm room, in case we came back to my room for fun.
Then to set her mind at ease, I ate some nachos and beer in front of her while she ate a girl salad and had some sort of fruity chick drink. She immediately thought I was a big strong man who liked to have fun and laugh (read: not a bodybuilder).
This works every time.
I've never once told a girl that I was successful with, that I was a bodybuilder. The times I have said "yeah, I do bodybuilding stuff" when I first met a girl, has invariably led to rejection. Girls do NOT like hearing that word, at least in my case. The only time you can unleash the "yeah I bodybuild" stuff is if your face is ridiculously handsome (mine is not) which allows you to do whatever you want, or you've been dating for a while and she's kind of started to really like you...then you can show her your FLEX magazine collection. She's already all-in and can't back out now.
When you show her your World Anabolic Review signed by the authors and your dog-eared copy of Bodyopus and your letter-to-the-editor that you got published in MuscleMag, expect to see the life drain out of her eyes, her shoulder sag in resignation, and her voice subtly quaver as she gently touches your arm and says "that's great...it's really awesome that you're so passionate about something. I love that about you!". At that point, you know you own her and she'll never leave. She might nag you to death, but she'll never leave.
I laugh about this all the time with my wife now. I say "sorry honey...you never had a chance!" She, of course, has her ways too. She "lost" my old bb'ing mags last time we moved. And she's thrown out every pair of gym clothes I've ever owned and bought me twink clothes (read: Abercrombie & Fitch t-shirts and some shitty stupid Adidas pants) for the gym. She says: "oh, you work so hard on your body...you should wear clothes that show it off". Meanwhile, I look like a dork and she knows it. So, it's give and take.