Yes, the chat can be embedded on web2 site: there is a tutorial on how to embed the chat at https://chat.peakd.com/docs/widget .
Now a question for you is: what is your actual use case? If you do embed it as shown in link above, your members (they do not have hive account right?) could still chat via guest accounts and participate with conversations in communities that allow guest accounts.
If the above is okay for your use case, it is very easy to embed it.
If you would like to create a chat space that would be only for your users and not users on hive, then you could run a backend messaging node that would not connect to the main network, you could then allow/disallow who can create guest accounts/further modify it. However, the current front-end is still quite dependent on hive communities as each hive-community represents a chatting community (which is not an issue if you'd need just one, you'd be able to create it or if you'd use a custom frontend, it would take more effort to add the ability for guests to create them).
Other than that, direct messages, group messages would work fine.