I think that the concept of Taichi, as a martial art is very clear for people who is practicing it for some years, and is close to Yang Family. But not everybody has this idea so clear. Most people has heard of Tai Chi as "something" like Yoga, very good for health, easy to learn,etc. And, as your old lady student, are not interested in learning how to fight. Maybe you have to separate classes, teach the same to the old ladies, but without showing applications, just the form (at least, at the begining). But this depends on how many classes you teach. Maybe you could give some classes for seniors and some regular classes for everyone who wants to learn Taichi as a whole.
I give a few classes a week, so I can´t split them. People who are not interested, simply give up. And in a natural process, I keep on teaching to people who is really interested.