It’s interesting reading the responses here, so FWIW..my two cents follows 🙂
It’s easy to respond from what we know and are familiar with, but things aren’t the same from parish to parish and diocese to diocese. And cultural traditions play a part too. Someone asked “who even has a party for First Communion” - well, let me introduce my Italian in-laws 🙂
If DD has been attending Mass, and prep hasn’t started yet, I’d don’t think you need be too worried that DD will be the odd one out. That’s why there is prep. If the parish priest is glad for her to be in the program, there’ll more than likely be other children from comparable circumstances. They’re kids, it’s about learning, it’s not likely they’ll be expected to know everything already.
Someone also mentioned a Catholic school will prep them. Ummmm…no, not always, that depends where you are in the world. While the sacraments will be dealt with in the RE program, specific prep might not take place at school. Some dioceses and parishes regard it as a parish and family responsibility and, particularly since covid, they may be quite a mix of ages and grade levels preparing. Some places do small group prep, others, like my own parish, do sessions with larger groups. DH has helped run them in our parish for years….at least one parent is required to attend, and while directed to the children, DH is always aware that he’s also talking to an audience of adults, some of whom aren’t Catholic or have been away for a while…..he’s always open to adult conversation and questions (not mid-session, obviously), hopefully your leaders / parish priest will be too, so you (and DH) should feel free to ask.
The dress…yeah, it shouldn’t be all about the dress, or the hair or the veil (not so many veils here these days, although some families still have them for their girls) or the shoes. I totally get not wanting her to feel the odd one out, but overspending should not be required. (I had boys, we just had to argue about wearing a tie! 😂)
Missals and rosary beads are nice traditional gifts, but the best gifts my sons received were beautiful framed photographs to hang on their wall (not specifically religious scenes) with some thoughtful, relevant messages, specific to them, written on the back by the giver. They’re all grown up now, and they don’t carry white-covered missals to Mass, but those pictures have gone with them and still hang in their bedrooms. It’s ok to think outside traditions.
All the best to your DD and to you and family for this special time. 🙏🏼