Keep in mind that any English saddle is acceptable at shows until FEI levels, where a Dressage saddle is required. So if her Antares is not specifically impeding her right now, she doesn’t necessarily need to rush out and buy a Dressage saddle to ride/learn Dressage. I’ve actually gotten better rider scores (admittedly at schooling shows) in my H/J saddle than I have in a previous Dressage saddle, so it’s just something to think about.
But if it is impeding her, I’d really make sure that you have the ability to try the saddles out under your trainer’s eye before committing to buy one. With neither you nor your daughter knowing much about Dressage, it would be really easy for you to think that because the saddle feels different to her it must be right, when it might be just as wrong a balance point as the Antares is.
FWIW, as a H/J rider who switched to Dressage for a while before starting to drift away again, I really like Passiers. The GG is good, but if that tips her forward, see if you can find a used Optimum II to try. I’m also a fan of Wintecs, although as others have noted, some horses hate the CAIR panels. My trainer jumps my guy in an Antares and he did well with the Passiers, so it might be worth starting there.