I recommend (or gift, or both)
So That's What They're For to all my friends when they're pregnant - it's humorous but factual, and it doesn't (IMO) come across in a heavy-handed way. So mothers who are 'not sure' don't feel judged by the book as they read it (but they're going to have good information to reduce their risks of sabotaging bf for themselves).
I also recommend
The Baby Book (Sears) for the same reason; it's APish, and has good science-based information in it moreso than say, the What to Expect books. And it assumes that the baby will be breastfed.
So, what I'd do if I were you, is gift her with both of those books (or recommend them to her early in the pregnancy, tell her you'll loan her your copies etc.). I think there's supposed to be a good one for mothers who work outside the home specifically too, if you anticipate that's what she'll be doing after baby arrives. Hopefully someone knows the title of that book ....
I also recommend
kellymom.com to everyone too - because her information is cited and quick to find late at night when a new mom is panicking!

In terms of the towel, just ignore it. Use it since you say you need more towels; if you have a machine and want to crop that part of the towel off (I'm assuming it's on a corner) - then do so. Send a nice "thank you" and don't worry.
I'd say she's so indoctrinated (as many people are) by the bottles = babies idea that she didn't even think about it when she bought it. She's likely to develop her knowledge in this area more, once she's nursing her own little one. Especially if she's watched you nursing your babe, she's going to probably have some goals in that area I'd hope.
