I think that you have unrealistic expectations, and that those unrealistic expectations are preventing you from addressing the real issues here.

the kids were not happy when I told them. Once she was born they became quite resentful about how she inconvenienced their lives, the main issue being my 17 r old and 15 year old share a room now, which they hate. It makes me sad that none of them are really close with her

They're teenagers. Of course they're not happy that a screaming, attention-sucking infant got dropped into their household. You can't expect them to be thrilled about getting a baby sibling and you definitely cannot expect them to share a true sibling bond with someone who will be wearing diapers and entering kindergarten when they are graduating high school. It's just not how the world works.

Especially when the arrival of that child has caused the forced room-sharing. I think you need to seriously look into a better solution because what you have come up with is clearly not working for the family.

I told my seventeen year old that I really needed to go to shopping, and it would make it easier if she could watch her sister.

Does babysitting make it easier for her? I can see how it makes your shopping easier. What effect does it have on your daughter?

When I was 17 I did not have the maturity necessary to take a step back and realize that something that inconveniences me was better for the family as a whole. Teenagers are naturally self-centered.

if I even ask them to watch her for five minutes, they do it begrudgingly after snapping that it isn't their responsibility and rolling their eyes.

I also want to point out that in your post you write that you want your kids to be close. How does this kind of childminding affect the relationship between your teenagers and your toddler? It seems to me like it's just breeding further resentment. I understand that it's very convenient for you to have them babysit, but sometimes convenience comes at a hidden cost.

I got mad at her for this

It's how she honestly feels, and I can empathize. You can get angry at her all you want over it, but it's not going to change anything and will only further reinforce to her that you're going to put the toddler over her any day of the week. (I am not saying that is accurate, but I'm trying to give you a picture of how this might look from her POV).

Your 17 year old knows that was a shitty thing to say, and that's why she said it. She's pissed at you and wants to make you angry in return.

Back to realistic and unrealistic expectations. Expecting a basic level of respect between all members of the household is realistic. That is where I would focus my efforts. Remove the major sources of resentment (room-sharing/babysitting) or find acceptable solutions that work for everybody and hammer down on being respectful by showing them that behaving maturely is what actually fixes things.

I was the toddler in this situation. What I can tell you is that no, the fact that my older siblings were annoyed with me as a young child did not cause any lasting harm. The lasting harm to the family unit was caused by the message my parents unintentionally sent to my older siblings. So that's my personal bias, right there.