There are several Aerith dresses and or costumes to unlock, 3 to be precise and getting them all will count towards the Dressed to the Nines trophy achievement which requires you to Obtain all nine bridal candidate outfits.
In order to unlock them you will need to complete 3 different requirements including;
Light Pink Dress – Complete zer0 Side Quests during Chapter 8 – Budding Bodyguard
Pink Dress – Complete 3 different side quests during Chapter 8 – Budding Bodyguard
Red Dress – Complete ALL side quests during Chapter 8 – Budding Bodyguard
Thus this may require a couple of playthroughs in order to unlock them all. The dresses will take effect during Chapter 9 – The Town that Never Sleeps.
You will also need to get all of the different Cloud and Tifa costume/dresses too in order to unlock the trophy achievement

Obtain all nine bridal candidate outfits.
Related Guides / Links:
- (FF7R) Final Fantasy VII Remake – Guides Playlist (Videos)
- (FF7R) Final Fantasy VII Remake – Guides Playlist (Written)
- (FF7R) Final Fantasy VII Remake – Game Review
- Lies Of P Wiki Contents - 18th September 2023
- All Chapter 2 Elysion Boulevard Collectibles – Lies Of P - 16th September 2023
- All Chapter 1 Collectibles – Lies Of P - 16th September 2023