Recent Successes:
Jessica Chastain, Saoirse Ronan! (TTM), Uzo Aduba, Laura Carmichael & Zawe Ashton (ip), Jane Horrocks, Gemma Arterton, Jim Broadbent, Lucy Liu, Christina Ricci, Andres Muschietti, Bill Skarsgard, and the cast of IT, Ian McKellen, Noomi Rapace (VV), MST3K/Rifftrax main cast (Mike Nelson, Bill Corbett, Kevin Murphy), Geddy Lee (ip)
IP: Shailene Woodley, Emma Stone, Jennifer Lawrence, Josh Hutcherson, Liam Hemsworth, Elizabeth Banks, Nina Jacobson, Sam Claflin, Jeffrey Wright, Elden Henson, Evan Ross, Douglas Booth, Logan Lerman, Andrew Garfield, Jamie Foxx, Jason Segel, Cameron Diaz, Dwayne 'The Rock' Johnson, Donald Sutherland, Johnny Depp, Jena Malone, Jamie Dornan, Dakota Johnson, Hugh Jackman, Theo James
Can't be certain because I wasn't there, but given the amount she must receive I would say it's highly unlikely. Her sig seems to change a lot, but usually it doesn't look too messy. It seems to usually have the big curly J and one swirly '8'. I'm sure others will tell you it's sec, but I'm just going by what Google shows me.
Recent Successes:
Jessica Chastain, Saoirse Ronan! (TTM), Uzo Aduba, Laura Carmichael & Zawe Ashton (ip), Jane Horrocks, Gemma Arterton, Jim Broadbent, Lucy Liu, Christina Ricci, Andres Muschietti, Bill Skarsgard, and the cast of IT, Ian McKellen, Noomi Rapace (VV), MST3K/Rifftrax main cast (Mike Nelson, Bill Corbett, Kevin Murphy), Geddy Lee (ip)
No one can ever be sure unless they watch her sign it but I would say it's a sec so no.
Favorite Successes: Walking Dead Cast(IP), Veronica Roth(IP), Rick Riordan(IP), All-American Rejects(IP), X-Men Days of Future Past Cast, Orphan Black Cast TTM Successes: James and Oliver Phelps, Matthew Lewis, Michael C. Hall, Willem Dafoe, Neil Patrick Harris, Daniel Radcliffe, Toni Collette, Rupert Grint, Miles Teller, Jake Gyllenhaal
You can tell easily by looking at the glare f the pic. If it is on paper and it is sparkly where she wrote then it is authentic. Jen is known for using sharpies markers on her autographs. It might sound weird, but when you first get it, you can sometimes tell if it is real by smelling it and seeing if it smells like Sharpie