Yeah, he keeps talking about the backups and so far there's been no mention of her in any of them. He has started mentioning she will be "appearing" in the Superman books until they go off world, and made it sound like she'll be in the Jon focused book when they split, but there's nothing concrete. Her appearance in the first issue was two pages with no speaking, so that isn't really a good use of her.
I'd actually be pretty shocked if Yang didn't end up using her in the Batman/Superman book. He's spoken several times how he was disappointed he didn't get to write Lois & Clark when he was working on New 52 Superman so I'd expect him to take advantage of that now. Red & Blue IDK. Jimmy is apparently getting his own chapter, so it would be kind of ridiculous for her not to be featured at all.
I also don't know that House of El works the way people assumed. These are all "El's" but I don't think they are all directly related to Clark & Jon. The refugees may end up taking the name "El" and becoming "adopted" members of the family. So the idea that these are all Clark's descendants is an interpretation from fans that I haven't seen come directly from PKJ or anyone else.