Crazy lady I rear ended going only 3kph at a red light nearly two years ago is sueing me for 250,000k

I’m in tears writing this.  I just received a long legal letter in the mail sueing me for an insane amount of money for an extremely minor accident I was in the fault for nearly two years ago.  It was just before a red light and it had been freezing rain, so very slippery roads.  Light turns red, lady in front slams on breaks and I attempt to stop but can’t, so I slowly slide forward, lightly bumping her back end, causing her to move ahead about a meter.  I was going no more than 3-5kph; no airbags went off or anything.  We exchanged information, and I observed that neither of our vehicles had any damage.  I could tell immediately, however, that this lady was slightly off her rocker.  She began calling and texting me nonstop, sending me paragraphs about how “I am locked out of my house and my sister has brain cancer and my neck hurts and my bumper is cracked and I am going to the doctor and “PLEASE WHEN CAN I CALL YOU??”  I notified my insurance immediately, sending them photos of my vehicle showing zero damage, and told her just to let insurance deal with it. The harassment luckily ended… or so I thought.  In the legal document she claims she had “SEVERE injuries to her neck, back and spine, WHIPLASH causing brain damage, loss of enjoyment of life,” and she even states I was driving dangerously which is NOT true at all, I had been driving extremely slowly and only couldn’t stop because of the road conditions.

The problem is it is her word against mine, as I did not take any photos of her vehicle, and there is no security footage of the accident since this is from almost two years ago.  What are the chances she will get a big payout from this?!  I am extremely frightened she will get doctors to lie for her in exchange for money. the letter came from a professional injury law office in my city and I am very scared.