Any texting is very unprofessional and you should say Something to her about it. As others have said the silence is normal and sound like a quote from my pdoc. You are supposed to lead the session, not the t. You may not be expressing the depth of importance of what you're saying to your t. So when she asks what else is going on, elaborate on what you were discussing if you need to. If the texting doesn't stop though, I'd ask for referrals to a new t.