she is not willing to sell it to a dealer for pennies on the dollar. There is some brass, tons of Athearn BB and similar, and lots of just plain junk.
Fair enough. Brass can be established through some reference book(s) and of course Mr. Zane could probably PM you a ball park figure as an experience brass guy if you can provide make, model, condition etc.
As for the rest, Athearn blue box and junk will not be worth a great deal - probably pennies on the dollar. To squeeze the maximum out of it is going to take a lot of time and patience. I'm sure you can get more money by avoiding someone who buys the whole lot. As nice as it is to step in and help, is there someone in your club that wants to help this person to that degree? It's going to take a lot of effort and time to squeeze more money out of blue box and junk.
Or, another option is to give her guidance and leave it up to her to do the work if she wants maximum dollar for that stuff, after all, it is her that wants the most money - so it's not fair to put a BIG job on a volunteer when she reeps the benefit, which may not end up being that much honestly. Knowledge and guidance, sure, thats reasonable. Anything beyond that may be well, up to the helper and how much time they have and how charitable they are feeling.
Having been to plenty of train shows, blue box Athearn and just plain junk is in massive quantity and low demand. Principles of economics are not in favor here. Thats the reality of it.
Speaking of train shows, that may be a good option for her. Have her rent table(s) and price items based on club advise and try to sell whats left though other means after that such as Ebay, HOswap lists etc. Items will have to be priced appropriately or she'll be sitting on it a long time.
I know one person near to where I live, Dean Ebner, who passed away about 7 years ago and he had a large nice collection of mostly ATSF oriented trains. That collection includede Intermountain, Athearn Genesis, Athearn RTR, Atlas, KATO, and similar brands and all priced very attractively (e.g. RTR Intermountain box cars NIB in the $8-$12 range). Deans widow and son had several large tables at Timonium probably 5 or 6 shows spanning around 2 years before selling the majority of the collection, and it was nice stuff, not Athearn blue box and junk. Timonium normally has quite a lot of Athearn blue box and junk trains so I'd imagine that level of stuff is hard to sell much of. There isn't much demand for it.