YANBU
I believe in a woman's right to make an informed choice about how they feed their baby. I believe in a woman's right to make different choices to me even if I don't understand them. Formula is a good thing, especially for those where BFing is not the right path for mental or physical reasons, either in advance or where BFing is not best serving the health of the baby or mother.
But I must admit, I find it strange when people just don't want to try BFing (I'm not meaning an underlying reason that is being kept private). You can't know how it will go in advance. Each mother is unique. Each baby is unique. I've managed to feed both of my babies beyond 6m, and the experiences have had different ups and downs, but the ups override the downs. Even as I wince as baby latches on to a nipple affected by thrush, there is something going on that I can't describe. It's not bonding as I don't believe that a FFed baby is any less bonded than a BFed baby. I suppose it's the pride that my body is continuing the job that it started in the uterus, and first time that gave me great comfort as I struggled to recover physically and mentally from a traumatic birth. I can understand feeling sad that someone has chosen not to have the chance to experience some of the unique feelings that accompany BFing.
It would be good if there was more balanced information about both feeding choices and combination feeding. It can be like being stuck between two parallel worlds of medical breast is best propaganda and the real world of advertising follow-on milk, shelves of formula in the baby zone of the supermarket, and family suggesting that a bottle of formula will help baby sleep through. It's sad when debates/ discussion get mired down in wounded feelings. Being more open about feeding methods and experiences is more likely to help people make informed decisions. There is a wider public health issue or the NHS wouldn't have policy on it and initiatives like the shopping vouchers discussed recently.
Other peoples' choices may not really be our buisness, but we are human and curious, and that's not necessarily a bad thing. The OP hasn't interefered, she's just considered her feelings about another person's choice.