Except she wasn't "cartoon-only."  She appeared in her own comic series prior to appearing in a couple of episodes of the All-New Superfriends Hour (the guest hero team-up segments); and, prior to that, appeared as a character in the novel Green Mansions, by WH Hudson.

If you enjoy the character, check out Kim Newman's novel The Angels of Music, by Kim Newman (author of the Anno Dracula series and the Diogenes Club books).  The concept began lfe as a couple of short stories in the Tales of the Shadowmen anthologies, edited by Jean-Marc and Randy Lofficier (Black Coat Books), which revolves around French pulp literature characters. Here, the gimmick is Charlie's Angels, but the unseen boss of the 3 female agents is Erik, the Phantom of the Opera, from the Gaton Leroux novel.  The three Angels were all from various literary works and the line-up changed between stories, with Rima part of a team that included Eliza Doolittle (who could impersonate any voice) and Gigi, as they infiltrate a hotel and casino, owned by Charles Foster Kane (who has the place rigged with surveillance cameras, set up by Dr Mabuse).  The novel version combines the two stories and then adds an additional history, at different points, linking the whole story.  Good stuff and Newman is terrific with this type of meta-fiction.