Looking for negative reference to women in the Avatamsaka Sutra I came across this rather gender progressive comment from Nichiren


  If we examine the Flower Garland Sutra, the first sutra to be preached
  after the Buddha attained enlightenment, we find that it is a Mahayana
  work preached by the Buddha in his aspect as the Thus Come One of the
  reward body. Thus, to the voice-hearers, cause-awakened ones, and
  others, it was like daytime to an owl or nighttime to a hawk; though
  they listened to it, it was as though they did so with deaf ears or
  blind eyes. This being the case, though people hoped that the sutra
  would enable them to pay back the four debts of gratitude, because it
  speaks disparagingly of women,3 it was hardly possible for them to
  repay the debt of gratitude owed to their mothers with the sutra.


which is footnoted with 


  3) For example, the Daishonin cites the passage “Women are messengers of
  hell who can destroy the seeds of Buddhahood. They may look like
  bodhisattvas, but at heart they are like yaksha demons” with regard to
  the Flower Garland Sutra. This passage is cited in A Collection of
  Treasures as a quotation from the Flower Garland Sutra.


http://www.nichirenlibrary.org/en/wnd-2/Content/264

I can't for the life of me find this or anything like it in my Cleary edition of the Avatamsaka. (I believe it is there, I've read all sorts of misogynistic passages in sutras, I just can't find it)
I downloaded the Chinese translation of the Avataṃsaka Sūtra and did a few searches for patterns with different combinations of words that are likely to appear there (e.g. 女 "woman", 地獄 "hell", 種 "seed", 夜叉 "Yaksha"). I found quite a few phrases, but none of them looked like the cited passage. My knowledge of classical Chinese is very rudimentary, so I may be mistaken. However, the search inside the Cleary translation on the Amazon website doesn't show any such passage either. So if it is there at all, I think it's more likely that the quote is a summary/paraphrase of a larger chunk of the sutra, and not a direct translation.

EDIT: I found a classical Chinese/classical Japanese phrase that is the source of your quote:


  女人地獄使。能断仏種子。外面似菩薩。内心如夜叉。


It can be found in this text at 7-094. Unfortunately, there is no information about the author nor the date when it was written. In any case, it is definitely not modern Japanese, so I don't think it was written recently. It seems to be a Nichiren commentary to the Lotus Sutra.

EDIT 2: The above quote is preceded by "華厳経云", which means "Avataṃsaka Sūtra says". That explains why the passage is commonly (and incorrectly, as we may conclude) attributed to this sutra.

EDIT 3: I found information about the origin of the quote, which, in light of the facts presented above, we can regard as conclusive:


  This statement is not found in the extant Chinese versions of the Flower Garland Sutra. However, A Collection of Treasures written by Taira no Yasuyori during the Jisho era (1177–1181) cites it as a quotation from the Flower Garland Sutra.