I would think someone was thinking of me and I would go, pay for my own lunch, bring a package of diapers and baby wipes, have fun and be happy.
What would you think if you recieved an invitation to a baby shower, at a local diner, asked to bring money for your own lunch (dutch), and the mommy only wants diapers and wipes?
If it was a second, or more, child, I would say the mom-to-be is looking for a day out without putting too much pressure on her friends. And gladly comply. I would find that an odd thing for a first child.
I would honor her request and enjoy the shower. Whatever makes her happy!
I would go, but bring my own boxed lunch and give her a highchair.
If this is her fourth child, she already knows what she's going to need. It is a little crass to have everyone go Dutch at a diner. That's the weird part. She could have had this at her home, provided lemonade, water and cookies. On the invite, she could have put - Mama needs diapers for the baby! - and called it good.
So I'm with you on the approach. However, as we wind our way in this world, there aren't many people out there with courtesy and manners and think nothing of manipulating people to get what they want. At least you know the diapers will go to good use. She could have had a link to an expensive baby site.
I would think someone was kind enough to think that I would want to join the celebration...and I would appreciate just being included.
 Showers (whether it be a bridal shower or baby shower is irrelevant) .. It's a gathering of support in honour of an event.
I think it's a great idea to throw an event like a shower to honour, celebrate and provide a gifting opportuntity for a new mother .. At no cost to anyone. There is nothing wrong with just being present at the event and gifting the new mother with such basic items .. In fact I think it is brilliant!
After attending a few baby showers myself. If someone invited me to theirs and only wanted me to buy my own food and throw them a pack of diapers and wipes I would say, Thank you! And honestly, diapers are one of the best gifts you can give the baby. If that's all she's asking for maybe she's already had things given to her or maybe she still has items from her other children (if she has any) and don't need anything else but diapers and wipes. Babies use A LOT of them. I guess I've been to too many showers where it feels like they want me to furnish the whole home..lol..so I would say I was lucky if I was just asked to bring diapers and buy my food.
When we have showers for the girls at work, we all go to a local restaurant each one of us buys her own meal and then everyone pitches in for the mother-to-be's meal. The weird thing is I've never gone to a baby shower for someone who is having their fourth child. Usually by then you have everything. But if they are strapped for money I see no reason why you shouldn't go and have a good time and give her whatever you can.
I feel kind of bad..... I have four kids and had a baby shower for each one. I thought thats what was suppose to happen. Now keep in mind I have four kids all expanding over a 20 year span. (My oldest was almost 18 when my youngest was born.) So safety features changed as well as recalls and regulations etc. But that doesn't help your situation. I LOVE the thoughts you have from all our friends Dragonfly. You all are so insightful.
On a side note, I think your friend is being reasonable. But no matter what please don't tell her you think it's "un-cooth" or that you have a problem with what she is expressing she wants/needs. When I got married my dad paid for my dress and provided the reception area. My husband and I paid for the rest. About a month before we got married my husband's company went under and laid off their workers so I sent out a kind note that if my guests were going to get us a gift, please can it be money towards rent and the honeymoon (we wanted to be kids again so we planned a day and a night at Magic Mountain...... Not the Bahamas! Lol) Anyways after we got back I was talking with my best friend.... Aka my maid of honor..... And she said it was a wonderful beautiful wedding but the only thing she didn't like was that I asked people for money for a gift. She said that was kind of rude and what if they wanted to buy me something instead. For some reason it stuck with me. I never knew if I was in the wrong but it kind of hurt. She of all people knew my situation. I wish she would have just left that last part out. It wasn't like I enjoyed having to ask. 😒