The dot doesn't matter to gmail. It matters to other services. Way back when I first learned about this feature, I registered for some website using first.last@gmail.com.
Unfortunately, when I later had to verify my account through email (as opposed to clicking a verification link) the website did not recognize firstlast@gmail.com (my sender address) as the account owner.
It does matter to Gmail, when signing in to its web interface (as opposed to email addressing and delivery). Or, it used to. Even though you could not create account names differing only by the presence or absence of a period, when it came time to sign in, you needed to use whatever variant you used when you created the account. (In my very limited experience, at least. Account created as xxx.yyy at gmail dot com needed to sign in to the web interface as xxx.yyy, Gmail would not accept xxxyyy as the user ID for the account.)
I'm surprised that she thought the right thing to do would be to post this instead of helping this other person.
She even said she received an email from the correct Sarah in 2008 so she knew exactly how to contact her, but instead she tried to log into her Photobucket account.
Unfortunately, when I later had to verify my account through email (as opposed to clicking a verification link) the website did not recognize firstlast@gmail.com (my sender address) as the account owner.