I am so excited for you both. Congrats!
I am a Syrian ham-parent and don't have any hybrids, but I understand that they are more prone to diabetes so you should take a little extra caution concerning her diet. From what other members with hybrids have mentioned, I would suggest avoiding any sugary/sweet treats including fruits. Stick to veggies but limit the sweeter veggies for a very rare treat. I believe many HCers feed their dwarfs a sugar/fruit free dwarf specific mix like Burgess Dwarf Hamster Harvest which I believe may be available in most pet shops & online. Also, hybrids tend to require a bit more protein in their diet than Syrians so you may want to try to supplement her diet with some mealworms. As far as how quickly to change her current food, I personally would make the change when you get her since you don't believe the one she is on is the best quality. I did that with my Eros, and she had no problem with the immediate change. I hope that this helps, and please don't ever feel concerned about asking questions. We all are here to help one another out as best as we can. Have fun with your new cutiepie tomorrow and just take the taming process one step at a time at her own pace. I look forward to getting to know her and seeing more pics whenever she is settled in more and you have a chance. Btw, Eros says hi and waves her tiny paw, too.