[8][9] McKeever, described as an environmental activist by Alannah Hopkin in her book West Cork: The People and the Place, was arrested in 2003 alongside Quentin Gargan for selling home produce on the street in Skibbereen.

[11] During the 2010s, Cairns lived abroad, spending some time working in an orphanage in Romania[12] before moving to Malta for four years.

There, Cairns worked for a charity organisation called INSPIRE which provides educational, therapeutic and leisure services to children and adults with intellectual, developmental and physical disabilities.

[12][13][14] Cairns first entered politics as an activist interested in LGBT rights, canvassing on behalf of David Norris during the 2011 Irish presidential election.

[25] She was reported by The Guardian to be running against her then boyfriend, Christopher O'Sullivan of the Fianna Fáil party, and as saying "I feel a bit like I'm in a badly written rom-com".

[31][32] In March 2020, the family farm organisation, the Irish Creamery Milk Suppliers Association (ICMSA), criticised Cairns for "airy-fairy criticism" of dairy export sectors.

Eileen Calnan, Chairperson of the West Cork ICMSA, said that she was "somewhat taken aback" by what she called Deputy Cairn's "lukewarm and half-hearted" support of the local dairy sector in an interview on RTÉ Radio 1's "Countrywide" programme.

[34] In April 2021, Cairns advocated to the Minister with responsibility for mental health, Mary Butler, on behalf of a constituent who feared she would die unless she could receive in-patient treatment for her anorexia and bulimia.

Cairns called on the government to remedy this, while her Social Democrats colleague Gary Gannon tabled a motion to ensure that funds already allocated for treating eating disorders are ring-fenced for that purpose and not siphoned off to other areas.

[35] In May 2021, she questioned the taoiseach, Micheál Martin, after he publicly encouraged An Taisce to withdraw an appeal against the construction of a €140 million cheese factory in County Kilkenny.

The bill was criticised for not facilitating access by survivors of the institutions to their personal data and maintaining the thirty-year seal of records from the commission's investigations.

[42] In November 2020, Cairns opposed a parliamentary motion to allocate state funding to the greyhound racing industry.

[47] Despite Cairns' lobbying, in 2021 the Fianna Fáil Minister for Agriculture Charlie McConalogue committed €19.2 million in taxpayer money to funding greyhound racing.

Nominations were due to close on 1 March, but none of the other TDs within the party chose to run in the election and as result she was announced as the new leader.

[54] Cairns is a proponent of Sláintecare, aiming for an "Irish NHS" to address the failures of the current healthcare system.

Cairns supports the idea of the church being held financially responsible for its historical wrongdoings, including using its land assets to compensate victims of clerical abuse and fund housing projects.

Cairns is critical of Direct Provision, acknowledging the necessity of adjusting the system due to the influx of refugees, but urging the government to set clear new targets.

Cairns supports transgender rights, advocating for self-identification and tailored approaches to issues like prison placement for trans individuals.

[55] Cairns has expressed support for Palestine,[56][57] accusing Israel of committing war crimes and encouraging Western leaders to call for a ceasefire.

Cairns believes Ireland should not facilitate violence and must adopt, in her view, a more principled stance in line with its neutrality and moral obligations.

She stated that social media pressure for Cairns and O'Sullivan to answer for each other's political decisions had affected their relationship.