Based upon the open source character Jenny Everywhere. Here we have her counterpart in Equestria, or her ponified after 'Shifting' into the land of ponies. The Shifter is one of her nicknames, due to her ability. Her cutie mark is an infinity symbol, representing her talent of being able to go anywhere in the omniverse.

http://en.wikipedia.org/wiki/Jenny_Everywhere

"The character of Jenny Everywhere is available for use by anyone, with only one condition: This paragraph must be included in any publication involving Jenny Everywhere, that others might use this property as they wish. All rights reversed."