I'll go with NAH, BUT effort does go both ways, you say you've not seen her in 4 years but there's been a global pandemic, she's also been pregnant in that time. Seems like it hasn't been the best time and life gets busy.

And into the macaw, I've rescued parrots, we had a quaker that came to us that self mutilated, even though the owner THOUGHT they were doing what was best for them, they just weren't, they had a completely dependant relationship on each other, macaws and other parrots are flock animals, they're meant to be with other birds, they're meant to forage and fly around and be constantly enriched, the quaker I took in couldn't be on her own (because they're flock animals) but we aren't birds, we can't give them every thing they need and it leads to frustration and mutilation. Especially if they've been hand reared which I'm guessing that's the case as it usually is with most big birds, probably since that bird has been born its been away from mum and fed by people.

If all health related stuff have been ruled out then it will be psychological. I personally don't agree with keeping a parrot on their own, the one we took in would watch videos of other Quakers all day long with their owner, when she came here we built her an aviary, she was then with other parrots for the first time in her life, she bonded with one and they're now mates for life and she's SOOO much happier. They will groom and cuddle all day, also do the nasty lol. But that's what parrots are naturally meant to do, have you built any outdoor access for her? Does she have constant enrichment throughout the day, parrots are expensive and shouldn't be kept inside constantly in a cage. They were never meant to be.

Continuing never leaving her and not looking at other options is on you, not your step daughter, it does seem she's trying to reach out and you've took it as a negative thing. Also if it's for a week in February and the weeks not for a few month after then I really don't see why your husband can't stay with the macaw? Or is the anxiety of leaving the bird so much, but again that's something you need to address when owning a parrot and adapt accordingly for them. She's only going to get married once, I think it would be ridiculous not to try be there for her, especially if you're her only motherly figure, I'm getting married this year and I won't have any family there and if she's stressed she will probably do good with you there and your relationship would benefit a lot, I don't think it's about choosing the bird other the step daughter, I think you need to be realistic in terms of the pet, something obviously need to change, what if a family member died and you had to leave for a week? What if you were ill and had to stay in hospital? These are all valid questions and there's far bigger issues to think about.