[3] From 2008 until 2017, Reimann was part of the leadership team of the SPD in Lower Saxony, under successive chairs Garrelt Duin (2007–2010), Olaf Lies (2010–2012) and Stephan Weil (2012–2017).

Ahead of the 2009 elections, German foreign minister Frank-Walter Steinmeier included her in his shadow cabinet of 10 women and eight men for the Social Democrats' campaign to unseat Chancellor Angela Merkel.

During her time in office, she notably led a cross-party initiative in 2015 for legislation on assisted suicide meant to absolve doctors from prosecution, alongside Peter Hintze and Lauterbach.

[6] In November 2017, Reimann resigned from parliament to accept her appointment as State Minister for Social Affairs, Health, and Equality in the cabinet of Minister-President Stephan Weil of Lower Saxony.

In the negotiations to form a coalition government under the leadership of Chancellor Angela Merkel following the 2017 federal elections, Reimann was again part of the working group on health policy, this time led by Hermann Gröhe, Georg Nüßlein and Malu Dreyer.