Sounds like you want to enchant it. In some circles this is also called consecrating it. It’s the same process as for any enchanted object, whether it’s your ritual tools, talismans or wards.
If you want to do this in a bit more detail, learn energy working so you can feel the energy, read it and adjust to suit.
- Cleanse it of unwanted energy, you can sweep the energy with your hands, visualising the unwanted, stagnant or unhelpful energy as black pieces being swept deep inti the Earth. Do that 3 times.
- Prepare your intentions and set up the feelings for the working. Visualise and feel how you will feel when she loves you. See this fill you and the whole room with no room for anything else.
- Hold out your hands palms facing the dress and feel your energy flowing from your palms to the dress, full of this image of her love for you.
- Finish with a statement of intent, “by my will, and if it be her will let X love me as much as I love her. And so it is.” Let your hands fall, let the dress sit undisturbed for a few hours before boxing it for gifting.
- Go outside and ground to clear yourself and remain balanced.