It would depend on how breastfeeding was going with the new baby. But then I don't like to pump so I wouldn't be as likely to do it.
I failed at breastfeeding my oldest (only made it 3 months) for several reasons and I have the same guilt. I wish u had done more and tried harder but I can't go back. She was 3 1/2 when DS was born so I didn't even think about trying to pump for her but even if I had wanted to it wouldn't have been easily attainable. I had a very rough nursing experience with DS because he was reflux, colic, and FTT even though I had more than enough milk. He was constantly sick, I had to pump between feeding and put that in an sNS to use when he nursed (long story) and I could go on and on. He finally weaned at 11 months because we had to start supplementing with elecare formula and he liked it better
With YDD nursing her was a dream (and she nursed until 18 months!!!!)
But I couldn't pump for DS because he can't tolerate dairy and soy and I didn't want to do an elimination diet when YDD didn't need it
The only time you should look in your neighbor's bowl is to make sure that they have enough. You don't look in your neighbor's bowl to see if you have as much as them.