The German, then 37, won the title last year when the women's tour returned to the venue after a 52-year absence. She was the oldest winner of a WTA 500 tournament.
But she had to come through the qualifying tournament this year after not receiving one of the four wildcards, all of which were handed to lower-ranked British players.
"It feels almost like a normal tournament because I had to start over again in qualifying," Maria, who was made an honorary life member at the London club after her title run last year, told BBC Sport.
"Already what I did last year was amazing and to be a champion here, I thought I deserved a wildcard and to get a little bit of respect."
Wildcards, awarded at organisers' discretion to players whose ranking does not merit main-draw entry, are often reserved for home players.
"I did it last year. It was not five years ago," said the world number 52, who is facing Greece's Maria Sakkari in the first round on Tuesday.
"I was surprised when I got the message of (tournament director) Laura Robson saying all the wildcards would go to the British players, which I understand. But as a champion, it's tough for me. It is something that should be normal. If you are champion of an event and you don't get in the year after, I think automatically this should be considered."
The wildcards went to Katie Boulter (ranked 73rd), Fran Jones (98th), Harriet Dart (160th), and Mika Stojsavljevic (261st).
A spokesperson for the Lawn Tennis Association (LTA) said: "The LTA owns and invests in staging these events for the benefit of the British game as a whole -- so fans can see world-class international players from around the world, and support our British players, but also so British players are afforded the playing opportunities to progress their careers and climb the rankings.
"We have seen British success at these events, and breakthrough wins, so there is clear value in giving British players these development opportunities."