Hi Clare! Welcome to the forum!
After only a week with you, it's likely that your new ham is still feeling insecure and nervous. That can come across as "aggression" but I promise you she is only trying to keep herself safe. It can take time for them to learn to trust you (especially since for a lot of hamsters from pet shops you will be their first human they have ever had any real contact with) and there are a lot of ways to do that, which I will briefly list in the order in which they should be tried!
- Tissue paper in your sleeve/ bra somewhere it will pick up your scent, give it to her to use for her nest
- Chatting to her softly through the bars of the cage so she gets used to your voice
- Offering treats from your finger tips
- Offering treats from the flat of your hand
- Stroke very lightly while she eats treat, come at her from in front so she can clearly see your hand approaching and choose to move away if she wants to
- Using treats to encourage her to walk onto your hand
You can see there is a process here and you can go into huuuuge detail on parts but that is the bare bones version. Just going straight to touching her when she is clearly not okay with it is not going to get us anywhere
Another note is that bar biting is usually a sign of stress and boredom, a lot of the time it can be because the cage is too small. If you post a pic or let us now which cage setup you're using we can possibly rule that out as a reason for her being so stressed out or point you towards some changes which might help her get settled.
Final note: You've done the right thing coming here for advice, you are not the first and won't be the last person to have these exact same issues. We can get you sorted