Wendy is one of Mavis' friends, that is helping her run the hotel their way. Wendy likes to like fun with her when she can, get a bit carried away at time when she is excited and can very honest at times, mostly with the slip of the tongue.
Wendy's After-Life Long Dream implies that like vampires (and mummies and zombies) that blobs are an undead species who are presently living an "after-life".
As a blob, Wendy can shift her shape into a lot of useful configurations. Some examples are pictured below:
Her viscous nature has some drawbacks. In Cries and Dolls for example they comment when she tries to wear a magic amulet in a game "the amulet is too heavy, and sinks right through her!"
Seeing him causes her to melt.
In Breakfast at Lydia's when Pedro yells "you should wear hats more Wendy, they really bring out your eyes!" she whispers "thank you" while holding her palms together.
In Cursery Rhymes when he expresses concern over leaving Blendy without a babysitter, Wendy comments "You left I tons of times and look how me well out it turned" (this is wrongly transcribed as "You left I tons of times and look how well me out it turned." in the closed captions) so she might have occasional grammar problems, or just be joking since she doesn't usually talk so strangely.
She eventually grows close with her stepmother, earning the status of "mummy by association" by the time of Talk Blobbish to Me
- In Bad Friday, it's revealed that she's the daughter of Blobby
- Wendy can actually speak English unlike the other blobs who just speak in the blob language