If you look around in most WarioWare fan circles, you'll notice that most of the focus is going towards only Ashley. Have these people actually played enough WarioWare games? Or are Ashley and her song their only exposure to it?
It makes you wonder, how many of her fans actually know anything about the series? Or even try to, for that matter? In fact, I'm surprised they managed to know about her at all.
It's like the Captain Falcon effect. He's popular for other reasons, but how many people who know about him know about F-Zero itself?
To be honest, it's hard to tell. On the one hand, a lot of the people who like the character do seem to have at least some level of familiarity with the rest of the series, there's an almost equally high amount of art and fan material featuring all WarioWare characters rather than just Ashley. For example, lots of group shots here:
https://www.google.co.uk/search?q=w...PY7WaoSXgKAG&ved=0CAgQ_AUoAQ&biw=1682&bih=807
Yeah there are a lot of Ashley fan pics here, but also a lot of general Wario cast ones...
Now, does that mean there aren't die hard Ashley fans who only care about her character or whatever? No. Indeed, to some degree, it's sort of similar to the situation with Rosalina, Midna and Krystal to some degree, they're all popular female characters from their respective series with a certain amount of fans who only seem to be interested in them specifically. Some maybe are interested in them a bit too much, like these people (from an affiliate's site):
http://wantmidnaback.com/
But that's only natural to some degree. Every franchise has a small subset of fans who are more fans of one character (or in live action works, actor/actress) rather than series. Like the small percentage of Doctor Who fangirls who mostly only cared about how 'cute' David Tennant or Matt Smith were.
The thing is though, they're pretty much always just a minority. To make another Doctor Who comparison, how many people actually stopped watching because the Doctor was played by the older Peter Capaldi? Very few. Were there some minor outcries by shallow morons on Facebook/Twitter/Tumblr? Probably, but they were mostly outnumbered by a very large group of people who kept enjoying the series based on the writing and universe and story and other stuff.
Same goes here with Ashley and her fanbase, as compared to the Wario one in general. There are a few people who only care about or have only heard of Ashley and her theme song, but they're only a very, very small minority. And if you need proof of that... well, ask yourself this:
Did Ashley's fanbase make even the smallest contribution to Game & Wario's sales? Cause she was pretty prominently featured in it, yet it still bombed hard. That doesn't happen if a character has a massive fanbase who likes them to the degree of other 'favourites' in other media. The people out there who like other similar characters at the expense of their main franchise will usually buy just about everything with them in it. For example, there's a reason why the Midna site mentioned went nuts for Hyrule Warriors...
Did her deconfirmation as playable in Smash Bros 4 do anything to the game's sales success? Of course not. The people whining about her not being playable are at best about 0.5% of Smash Bros 4 fans, and are outnumbered by an order of magnitude by the fanboys and fangirls for characters like King K Rool and Ridley.
Basically, the type of Ashley fans you hint at, don't really exist in a significant number. If I put a poll up on DeviantArt or Tumblr asking the following questions:
1. Do you like Ashley (WarioWare series)?
2. Are you a Wario fan?
3. Do you buy Wario games where Ashley isn't present?
Then I bet the results would be that just about no one would say yes to the first and no to the last two questions.
The only reason a lot of focus is going towards Ashley is general character popularity among WarioWare fans. It's like how most Mario & Luigi fan art is all about the villains (like Antasma or Fawful) or the ensemble darkhorse non villains (like Kylie Koopa, Popple or the Massif Bros). No one out there is going to be a Fawful or Antasma fan who knows nothing about the Mario & Luigi series.