This, actually, sounds like a "happy" ending to me meaning that this is as happy as a therapy where intense transference was involved can get.

Her pain seems natural. It doesn't sound like trauma caused by the clumsy handling of transference by a therapist, which is what I hear most from people. This experience sounds like a natural loss of someone you loved intensely and who was important to you..for 12 weeks.

I suspect, this was a success precisely because the therapy didn't last more than 12 weeks. It was focused and goal-oriented and when the objectives were met, it was ended. Seems perfect to me. If she tried to "work through" her transference and stayed longer, she'd end up traumatized and messed up like so many people here on PC who see their therapists for years.