Hi Jaana
I'm not an expert at Halle's autograph, but I don't think the autograph is authentic.
By the looks of the autograph, it appears that someone may have tried to sign it as "Halley" as the last part of the autograph appears to be a Y.
Her IP autograph generally resembles her SFM autograph. However, the example you posted varies considerably to her SFM autograph:
Picture taken from egiblock's SFM success
nowandagain [rockon]