I got a signed card from her ttm in 1997 and the signature looks just perfectly as the one on your picture. As far as I know she didn't have a secretary, so yours should be authentic.
Thanks, KaiMi! I did win it. Unfortunately, she was one of the last lots and I did not know how much I would have to spend - so I did not bid on a gorgeous Grace Kelly or Doris Day. But I am super happy with Maureen!!