It's really not uncommon for people (attending or not) to send gifts in advance to the couple's house. The more gifts that people bring to the actual wedding, the more that has to be moved back to their house after the wedding. Since a lot of couples leave the wedding, head right to a hotel, and leave from the hotel for their honeymoon the next day, it's a friend or family member responsible for transporting all the gifts brought to the wedding, which means the gifts realistically may not be opened until after they return from their honeymoon (assuming they take one).
I think you'd be fine giving it to her before the wedding.
