That is absolutely no excuse for her to not bring this to your attention much, much sooner, so you’d know what options were available to you.

She needs to pursue this with your insurance company. If they still refuse to pay, and she expects you to pay, she needs to work out a payment plan that works for YOU, because you’re the one getting screwed over here.

If I were the practitioner (I wouldn’t have let this happen, but pretend I did) there’s no way I would hold you accountable for 11 months worth of sessions. I would tell you that you need to pay going forward, but I’d write it off as a loss because I made a really stupid business move by not addressing it sooner.

Do you know how many sessions you had and what her rate is per session?