If the e-mail is from "onlinegame(at)hellokitty.com" then you can consider it safe, and if necessary, divulge certain personal information. As always, be wise; it's not just your account information, but your identity, that is at stake when it comes to scams.
If you are not on the master list, you should not be receiving e-mails about beta testing at all.
Although Abby promises that all information that you send them will be kept private, it is important to note that if your e-mail address ever appears in print it will appear partially, so that you will never be hounded by spambots. As much of a fan as I am, I'd like to keep my inbox free of "Keroppi enlargement" advertisements, thanks (we've all been there).
Have you received any curious or suspicious e-mails purporting to be official? If so, remember to click "report as phishing scam" with your e-mail service provider.