If the shower is a surprise, I don't see how it could possibly come across as "gift-grabby" or like the mom is angling for things for a boy because she was a 'poor planner' in her first pregnancy. It doesn't sound like she's asking for this, but a good friend was just looking for a way to show love and support the second time around.
There were other good ideas given for doing that without doing a shower, but I for one don't think throwing an intimate party to celebrate something great in a friend's life can ever be a bad thing. I had a neighbor who already had a child (daughter) before she moved to the neighborhood, and was expecting, and I threw her a surprise neighborhood shower because she was going through a lot of loneliness and depression during her second pregnancy and I wanted to show her the support she had surrounding her even though her family wasn't close by. It meant the WORLD to her, and those who came understood that the intention wasn't to supply her with every baby thing she probably got the first time around, but just to have fun and hang out and if they felt moved to buy a little onesie for her son-to-be or wrap up a hand-me-down toy from their children, so be it. I made clear in the invites (it was a very small gathering) that the intention was to gather to celebrate and gifts were not expected in any way, and I decorated with all boy/gender neutral clothing items from Once Upon a Child (new, but WAY cheap!) on a clothesline around the room, and she got to take those home with her at the end. Other than that, and I think a hand-me-down from another guest, I can't even remember if anyone else brought a gift, but I do remember the food, laughing a ton, and her husband thanking me profusely for doing it for her, b/c she had been in tears the night before and came home feeling so encouraged.
If you want to celebrate someone/someone's baby, do it!! :-)