I see no one has responded to your post, so I will.
There is no way generally to determine who she signed what for. Most of that material would be numbered and limited (1/100, 2/100 etc) and possibly marked as signed for so-and-so. Perhaps one might say the signature looked fine - if one could actually see it - but the seller chose not show a large enough scan to make any reasonable determination possible. It would be incredibly
irresponsible of me to authenticate your item from anything less than a very good large scan. What I see in the auction could be anything.
The seller - well, his feedback is atrocious in my opinion. Go to Toolhaus.org and enter the sellers ID and wait about 5 minutes. You's get more results but the thing times out there is so much to see. He does not appear to have specific feedback for forgery, but seems very fond of selling damaged pre-prints, Auto-pens and other misrepresented items - but you can make that determination when you read his feedback. I would be VERY interested to see the Sean Connery he sold for $8.95 when a genuine example is worth much, much more...This seller is not a person I would ever go near. His "proof photo" is fully meaningless unless it can be demonstrated factually and visually that Miss Dean is holding the exact same signed photo you have purchased - not one "just like it" from a single sitting where she may have signed 200. This is a generic photo - these are often used by unscrupulous sellers...for the obvious effect. I looked at some of his other offerings and some appear genuine, but from these low quality scans one wonders who his target market is. No one versed in buying autographs would buy from his images. Also, the "proof photo" she is holding in his auction image appears unsigned anyway, but again, from such a small image one can't say. Why didn't you buy from a reputable dealer who would be very happy to supply the COA you wanted in the first place? Her signature is not rare or even scarce by any definition.
Never blindly rely on any COA - I will not sell anything to people who "need" a COA - I suggest they educate themselves instead of making a sale. This education is valuable - you don't want it to be expensive!
It takes a long time and a LOT of experience to become adept in this field - it is a lot more than "it looks like it." I do understand you are likely not setting out to start collecting autographs and you just want some assurance (SMART!) - so: Options:
1) Return the item as you are within the return period and buy from a reputable dealer. Any COA from this person would be of no value at all (buy one with a COA if you must have one, and buy from a reputable dealer who will back the item for life and supply contact information). Be warned though, a COA is worthless - the seller behind the COA is what really matters. Any fool can print a COA, especially if they are willing to forge a signature. I see this seller also is fond of charging extra $ for COA's - a practice that is...unspeakable!
2) Submit your item to an authentication service. This would probably cost as much or more then you paid for the item (plus shipping and insurance both ways), and such papers will mean nothing to some, like me, based on material I have seen "pass" before.
3) Scan your signed photograph at good resolution, post it here and and hopefully Tim.T., Achmet P. (and I certainly) could look at it for you. Speaking of the two gentleman whose initials I mentioned, you could not do better. Any knowledgeable purchaser of such an item in the future will not need any COA - all that matters in the signature and its characteristics. This is my suggestion.
I post my own Millvina Dean signed photo for you (this was signed in the last months of her life (last week of September, 2008) and will appear a bit different from earlier examples):Hand tinted unique candid taken photograph aboard the R.M.S. Adriatic, signed to me personally by Miss Millvina Dean, youngest and last survivor of the Titanic. "To Eric with all good wishes from Millvina Dean, youngest and last survivor of the Titanic"
The Adriatic took Miss Dean, her mother and brother back to England after the Titanic disaster. Five years earlier, in 1907, Titanic's Captain Smith brought the Adriatic over on her maiden voyage. He was interviewed in New York and said "...I never saw a wreck and have never been wrecked, nor was I ever in any predicament that threatened to end in disaster of any sort." - May 16, 1907. ALL Thanks due to "a friend"
I hope this has been helpful