Friends that don’t get it

Does anyone else find that their friends without babies just don’t get it I have a friend that’s pressuring me to come to her birthday outing in the evening/night time and I’ve explained that I can’t afford it because maternity pay is horrible and it’s Christmas etc, also I’m breastfeeding and if my husbands working I don’t have childcare and I would definitely do something in the day time with her another day to celebrate. but she’s still saying I don’t have to bowl or come for the meal so not to spend money but she wants me there and I’ve explained that I can’t go. she then told me to just bring my son but doesn’t understand how stressful it is to change the routine we’ve just got into and by the evening I’m absolutely exhausted! I really don’t know what more I can say when I’ve explained it multiple times that I just won’t be able to make that occasion. I then had messages from her sister and one of her other friends (who I don’t even know btw) What more can I do to stop everyone hounding me about it?!