On the contrary, “seminary” is the generally accepted English translation for “yeshiva”. It is a somewhat inadequate translation, because a seminary is generally a place where religious officials are trained, so it carries the implication that it exists to train Rabbis, unlike the idea of learning l’shmah. However, “seminary” can simply mean a place where religion or theology is studied.
As far as I can tell, the use of “seminary” for Jewish female educational institutes is the same as the first sense above: a school which trains religious teachers. In this sense it’s short for “teacher’s seminary.” In fact, some schools such as Gateshead have “Teacher’s Seminary” as part of their name.
Nowadays, it seems that the majority of female seminary graduates do not go into teaching, and some seminaries offer different tracks to students who want a teacher’s certificate, so “seminary” is being used in pretty much the same sense it would be used to describe a yeshiva: a place where religion and religious texts are studied.