In my experience, sometimes therapists are weird about boundaries. My thought is that if the therapist is doing an effective job, not too many emails should have to be sent. But if someone is really struggling, I feel like not replying to emails is not good, unless it's counterproductive to some issue that the client is working on in therapy. My idea is to talk directly to your therapist in your next session in person, (or virtual, most likely), but tell her how you feel about this. Tell her exactly what you said here. It's good to ask directly about things like this, in my experience. Say something like, I don't understand why you aren't responding to emails anymore. It makes me feel... when you do this.