Two sides are weighing in here:
1. Tell her the truth. Truth is the foundation of any strong relationship.
2. Suck it up -- stay quiet. Don't hurt her feelings -- be sensitive.
A lot of merit on both sides. You need to do both, and here's how.
First of all, think deeper. As you said yourself, you might need better bath products, and your gf might be making a suggestion. Second, study Lush. Pretty interesting and responsible company it seems. And hey, your gf is "in" to it, so why shouldn't you expand your world a bit and "expose" yourself to their products (sorry about the pun -- couldn't help it).
After all, shared interests, or at least mutual respect for each other's interests, ranks up their with truth in importance to a relationship, and is probabaly just below having the hots for each other as the key glue to making it last. Hey -- my world changed when I got the Denon D2000's on my wife's head and she finally understood, and now supports, my hobby!
So with an open mind, respect for what Lush stands for, a desire to understand your gf's interest, a goal of sharing something, and (last but not least) appreciation for her gift, for what she did, for the thinking she put in to it -- USE THE STUFF, at least once.
If you feel the need to not use it, or sell it on eBay, then dude you do not love this girl and move on. Dig down. You should, somewhere in your soul, WANT to use it. Maybe deep, but if you don't have this desire anywhere then you fail a fundamental feeling for your gf. Sorry to be blunt.
OK, so you do want to try and see the world her way, you do want to learn what makes her tick, understand why she would enjoy this, and share more, and you do use it.
Now you tell the truth. "Honey, at first I was a bit surprised ... I mean I think of myself as 40 Mule Garage Hand Cleaner, not Lush. But you love this stuff, and I love you ... so I tried it last night."
Continue with more truth: "To be honest, I didn't really like it" or "To be honest, it was fine, but no different for me than Dial soap" or "Who would have guessed, but it is really great".
And then (especially if your reaction is negative): "I took the time to read more about Lush than I had before, and I was impressed with their ethics and policies. Pretty neat, and I see why you like them, and I like you because you like them"
My hope is that you really had all this figured out on your own, 'cause your smarter than me ... it took one spectacularly failed marriage of 14 years for me to understand what makes a relationship work, stayed single for 14 more years on purpose, and now am in the 12th year of a spectacularly successful marriage, for which I give thanks every day. Except she hogs the Denons.
