I think it's good you're able to recognize that your therapist's comment was not aimed at you. Many, many therapists are overwhelmed right now because people are needier than normal: people are leaving more emails, texts, and voicemails than they typically do, and they are requesting more frequent or additional appointments. So, to be honest, she probably has certain clients overloading her inboxes, and it's gotten to the point where she has no choice but to say, "I don't have the time," to every one of her patients. She just cannot keep up if certain people are blowing up her inboxes. So, the problem is not you yourself, but the combination of many factors that have nothing to do with you. But on the upside, I think it is best she tells you she cannot respond, as opposed to just outright ignoring your emails or "taking too long" to respond.