Check only email?

I have a quick question…

I have my comments set up so that I have to approve the *first* comment someone makes. If someone gets a comment approved, then (supposedly) I don’t have to moderate their comments anymore.

So what I’m wondering is this: my sister loves to come to my site an leaves comments. She *always* uses the same email address, but she also likes to change the name.

Every single comments she leaves, I have to approve, every time. Is it because she keeps changing the name in the “Name” field, and it sees her as someone new?

If so, can I “whitelist” her somehow by email address only? Or change it so WP only has to check the email field and IP address (rather than name and email)?

Just wondering 🙂 I know I can always tell her to quit trying to fake me out, ’cause I know who it is.