All purchased content is tied to the Apple ID that was used to purchase it. If you create a new account, you will not be able to use the purchased content with that Apple ID.
Why do you have to creat a new iTunes account? If you got a new email address you can change the username associated with the Apple ID and you don't have to create a new account.
Since you can't "split" iTunes accounts, you'll have to decide with your daughter whether she keeps the account and all the purchases, or if you keep it and she gets a new account. For example, if she hasn't bought much on her account, you could have her get a new account and pay for her to repurchase those items.
I hope this isn't too wordy but I want to be as clear and explicit as I can for you.
You can't transfer purchases from one account to another account. Apple doesn't allow it.
You can continue to use your daughter's Apple ID in order to continue to use the apps that you purchased with her ID and you will need to use her ID and password any time that you want to update those apps. What you do want to avoid is having to download any of those purchased apps again on any other devices - if you create a new Apple ID.
If you create a new ID and then you sign into her ID in order to download a previous purchase- you will lock yourself out of the new ID for 90 days and there is nothing that you can do about it. So as long as you do NOT download any past purchases with her ID - you will not lock yourself out of the new ID. So you can keep using the apps that were bought with her ID, you can also update those apps using her ID (you have to sign into her account in Settings>Store) but you can't download past purchases without messing things up with your new ID.
When you download a past purchase with a different ID - you associate that device with the different ID for 90 days. This is one way that Apple hopes to cut down on pirating of apps - friends using other friends IDs in order to download apps without patting for them.
This explains it in a little more detail.
The bottom line is that you can create a new ID, still use her ID - judiciously - but you really want to avoid downloading past purchases with her ID. Transfer all of those purchases into iTunes so that if something happens and you need the purchased content again, you can just sync it again rather than downloading it.
This explains transferring purchases.