No, that is not correct.
Strictly speaking, only Frederik can act as Regent.
According to this (unfortunately Danish) wikipedia page Rigsforstander - Wikipedia, den frie encyklopædi Princess Elisabeth cannot act as rigsforstander (well, at least she isn't mentioned and I can't remember she ever has).
The Bernadotte family reunion in June 2005 (at Sofiero castle) was not attended by Princess Benedikte (and I can't remember Queen Anne-Marie either), which means that she most probably acted as rigsforstander while the Queen, Frederik and Joachim were in Sweden.
Strictly speaking, only Frederik can act as Regent.
His brother Joachim and Princess Benedikte can act as "rigsforstander".H.K.H. Kronprinsen er regent i perioden 8.-28. august
H.K.H. Prins Joachim er rigsforstander i perioden 31. oktober - 9. november.
According to this (unfortunately Danish) wikipedia page Rigsforstander - Wikipedia, den frie encyklopædi Princess Elisabeth cannot act as rigsforstander (well, at least she isn't mentioned and I can't remember she ever has).
The Bernadotte family reunion in June 2005 (at Sofiero castle) was not attended by Princess Benedikte (and I can't remember Queen Anne-Marie either), which means that she most probably acted as rigsforstander while the Queen, Frederik and Joachim were in Sweden.