I would for sure bring a stroller. They'll want it for port and even moving around the ship. I would not suggest a full sized one. We always had a fancy umbrella.
We cruised with our son at 7 months (a different line) and 10 months on Disney.
For food we did a combination of jarred food that we brought and some of the food they provided. And I don't worry about the water now but we did worry when he was an infant so we also brought a case of water for us. We just brought a nearly empty carry on and then stopped at the store on the way to the port and got water and baby food. They we wheeled it on in the carry on.
They make disposable bibs that are so easy for travel. It is one more thing to pack but it's worth it. Also have her count the number of diapers she uses in a day, bring that many and then bring some extras. We also bring little pods for washing clothes mid cruise in case that is necessary. We also liked those disposable placemats that could be stuck on the table. At lunch and where there were table clothes we would use this since they aren't really eating off plates at this stage. At least I don't recall my kid doing that.
She should bring swim diapers because she can take the baby in the little splash pad on the ship.
Babyganics has an alcohol free hand sanitizer that we used then and still use. They have individually packed hand wipes, plus a foam liquid pump (including travel sizes that you can get from
Amazon). We used that to wipe his hands after he'd crawl on the ground. And just before meals and stuff. We love it.
My son would get motion sick in the car so we also bought motionease for the cruises. It's a combination of essential oils used to prevent motion sickness. You just put it behind their ears.
My son wouldn't sleep at night in the stroller so that just meant that we missed the shows. They do show them on tv. We would keep him on his normal schedule in order to have a happier baby.
They can download on their phones a white noise app to make some background noise which will cover up little ship noises that might make it hard for the baby to sleep.
feel free to ask other questions. My kiddo is only 3 so his infant cruises are still fresh-ish in my mind!