Why did her career never really take off?

Because she doesn't have any range beyond "obnoxious geek girl" and "milquetoast geek girl"

She's a Mad in the MST3K

...

I don't think she really wanted to become an actress. I think she totally embrassed her geek side and made a business out of it.

no she really, really wants to be an actress.
She goes for auditions all the time and sends her own scripts to tv companies all the time.
She just never gets anything so she relies on her nerd persona to make money

T H I C C

pretty much this, you would be surprised number of events she attends hoping to make network connections.

I think mostly it's because some producers and directors only see her as this cute thing that could only play one role. Maybe they are right.

She's typecast as a geeky gamer girl but has long outgrown the appropriate age to play such a character.

...

She just needs to get over this hump.

not talented enough

She farts a lot.

>Massively loyal fanbase
She has a small following. I wouldn't even call it a "cult following."

>Brings in massive ratings whenever she's on a show
Proof of this? I can't say whether or not that's true.

>Friends with Joss Whedon and inspired Dr Horrible's Sing Along Blog
Lots of people whose careers died are friends with Joss Whedon.

>Why did her career never really take off?
1. She was never that pretty and has become less pretty as she's aged.

2. Most people don't know who she is.

3. She's not great actress.