Summer Gleeson has not appeared in the mainstream DC Comics, however she does seem to be based upon Vicki Vale, an existing character with many traits in common but enough differences between them. These traits include both being redheads, both being some form of reporter and both of them knowing Bruce Wayne personally. The main difference between the two is that Summer, unlike Vicki, has never been romantically involved with Bruce Wayne and only knows him as an acquaintance.
Although she has not appeared in the comics, there was a mention of her name in the No Man's Land series.
Despite her absence from the later "new look" episodes of Batman: The Animated Series (outside of a few, brief cameos), the official website for "The New Batman-Superman Adventures" refers to Summer as Jack Ryder's Gotham Insider co-host.