You are not being selfish - but she is, massively so. Massively massively so.
This is something you need to thrash out before you go a step further with ttc, because if she is already showing insecurity and jealousy around the fact that you will have the birth mother role, then you really should hold fire for now.
I think her feelings sound completely understandable, but if that's how she feels, this is a recipe for disaster. Because for your baby to have the best start, a 'special bond' is completely necessary, and ideally that would include breastfeeding and a strong one-on-one relationship: a primary carer role. And yes you can express, but ideally not from day one and your first focus should be on establishing bf with the baby: you holding and feeding baby pretty much 24/7 on demand. If she's going to not be able to handle this, you CANNOT go ahead: you cannot have an insecure, unsupportive partner wrecking the newborn phase: it will be awful for all three of you.
This is of course what dads have to handle and I think it can be very hard: but that's parenting! Putting the baby's needs first. FWIW I bf forever and was surgically attached to mine for the first few months: now, DH and I have exactly the same strength of 'bond' and it's never been an issue. But it's hard and can create terrible feelings of insecurity at first, being the non-birthing, non-feeding parent.
I think it's a great idea to look into whether she could lactate, but I think the issues sound a bit more deep-rooted than just bf, and I think you need to spend a bit of time tackling them. Bottom line: your baby cannot be denied an optimum level of security, bonding and feeding simply to pander to your partner's insecurity. If she can't get that, then no, she will not currently be able to be a good parent.