No I think she has time limit.
There was a video long ago, which stated "during the planning process we asked those type of questions, should violet be able to be invisible all the time or not" or something along those lines.
Yeah her abilities have been Improved, in the game she is "grown up" and avalanche worked with Pixar to come up with the idea she is older and wiser and has improved and advanced her powers.
We have the freedom of speech!!!