The Monopoly game came out months ago, back when the advertisement tried to convince us that Finn was the new main good guy Jedi. It is also not a Force Awakens Monompoly, but simply a Star Wars one.
Plus, this is a licensed collector orientated Monopoly, with only four pieces, guess what's going to happen, they'll release the same version with different pieces every couple of months. They did the same with the Transformers Monopoly, each version with a different set of characters so you had to get all if you wanted all of the (actually really nicely done pieces). The next set will contain Rey, and three other characters, and the set after that will contain others characters again, it's how this works.
As for the amount of Rey action figures, she gets the same amount as anyone else (save main Stormtroopers, toy collectors love army building which means cash money!), she was part of trying to conceal spoilers for the movie though. A guy got sued because he found and bought a Rey action figure that was put out before its street date, he posted a photo of it and got his ass sued. The action figure was of Rey with the Anakin Lightsaber.
As for missing in action figure sets, she can't be in all, and it's extremely difficult in this case, the one that gets pointed out the most contains three figures of each side, Keylo Ren (the main bad guy who's the face of the toy packaging, they're trying to make this the new Darth Vader) Two different Troopers (army building is fun and troopers are the easiest to make with the most profit), Chewbacca (important beloved legacy retro character, to justify people buying the set), Finn (the advertisements "main character", excluding him would have resulted in accusations of racism), and Poe (excluding him would also lead to accusations of racism, what the white girl is included, but not the Latin guy?). Seriously they can't win here.
BB8 is so prevalent because he's designed to be the kid appeal character, he's a cute, funny little R2D2 like robot that makes cute funny noises, so he gets lots of merch.
As for playsets, guess what, Hasbro wants you to buy all of the playsets, which is why you won't find every character, even important ones in all of them. Yes, she's missing from the Millenium Falcon, but so is Han Solo, the owner and most iconic character associated with that ship. She's already available in a set featuring her speeder thing.
But yes, she gets just as many figures as everyone else, she is present in every product range of the toy line, save for the giant Darth Vader ones. I know, I spend hours looking through all of them trying to find R2D2 an C3P0, they only had a shitty two pack.
And to those comparing this to the Black Widow thing from Age of Ultron, you know why she had so little toys in that movie? It was because the Black Widow figures for the first Avengers movie sold so badly that they were still taking up shelf space when Age of Ultron came around. She was a commercial failure for the first toy line, so she was reduced in the second basically just there because she was an important part of the movie and had to be done.