I have a crush on a girl, but she's already in a long relationship

I met this girl at work, I think i have a huge crush on her. The thing is she is in a 7 years relationship. Talking to her makes me happy.

Fact: it's been years since i felt romantic to a girl, i just want to indulge myself, and give it a shot.

Problem: I don't want to be the bad guy who ruins a relationship.

How she feels: I'm slowly giving her hint that i like her, but it seems she see's me as a friend only.

What i want to do: I just want to know her more, and let her know how i feel, and see where this will lead me.

My plan: This coming valentines i want to give her flower (Not that extravagant, maybe a single rose not a bouquet) and an anonymous note, just give her a little hint that it's from me.

Should i still go for it? what do you think she will feel and think about me? Need some advice. especially to a girl stand point. Thanks

If she's with someone for 7 years, she loves them. Period. NO VALENTINE'S DAY SURPRISE! If you want to get to know her, BE HER FRIEND. That's IT! And if you pull some shit on V-Day, she most likely won't even want to be your friend. Be her friend, if there's ANY chance of her liking you, and one day leaving her man for you, it won't be by someone who doesn't respect the fact that she's in a relationship. Be her friend.

No, don't go for it, she is in a relationship so go find someone single & give them v-day wishes instead.