The claims are that Tamiflu will only lessen symptoms by 12 hours or less. It doesn't cure the flu or treat it.
The best prevention is Vitamin D and Vitamin C. If she would get the flu, you could probably use NSAIDS if her counts are over 50k at the time. I'd check with her doctors.

www.ncbi.nlm.nih.gov/m/pubmed/22156085/
www.ncbi.nlm.nih.gov/pmc/articles/PMC4375804/?fbclid=IwAR3L3AInpwratszGs5Lp-yGksVMNB8GWhNdCHlM1TbbBtzA8cg145tzCHrk

"But as Jeanne Lenzer, an independent reporter and associate editor at the medical journal BMJ points out in a recent article, there’s a big problem with Frieden’s advice: The Food and Drug Administration (FDA) has determined that the clinical trial data submitted to it for review does not support the claim that Tamiflu “saves lives” or even reduces hospitalizations, including for the elderly and others most at risk."

www.minnpost.com/second-opinion/2015/02/cdcs-advice-take-tamiflu-compromised-financial-conflicts-interest/?fbclid=IwAR3ha_iuoMxLrwFa53y6w_9gQpZ-K2-W_0IQr5gbRLzqyj71vEH8359mZpI

And yet, they are still prescribing it.

"Oseltamivir (Tamiflu), a neuraminidase inhibitor, was approved for seasonal flu by US Food and Drug Administration in 1999. A number of randomized controlled trials, systematic reviews, and meta-analysis emphasized a favorable efficacy and safety profile. Majority of them were funded by Roche, which also first marketed and promoted this drug. In 2005 and 2009, the looming fear of pandemic flu led to recommendation by prominent regulatory bodies such as World Health Organization (WHO), Centers for Disease Control and Prevention, European Medicines Agency and others for its use in treatment and prophylaxis of influenza, and it's stockpiling as a measure to tide over the crisis. Serious Adverse Events, especially neuropsychiatric events associated with Tamiflu started getting reported leading to a cascade of questions on clinical utility of this drug. A recent Cochrane review and related articles have questioned the risk-benefit ratio of the drug, besides raising doubts about the regulatory decision of approving it. The recommendations for stockpiling the said drug as given by various international organizations viz WHO have also been put to scrutiny. Although many reviewers have labeled the Tamiflu saga as a “costly mistake,” the episode leaves us with some important lessons. This article takes a comprehensive relook on the subject, and we proceed to suggest some ways and means to avoid a similar situation in the future."

www.ncbi.nlm.nih.gov/pmc/articles/PMC4375804/?fbclid=IwAR3L3AInpwratszGs5Lp-yGksVMNB8GWhNdCHlM1TbbBtzA8cg145tzCHrk

I thought you guys might want to be aware of this:

OBJECTIVE: To examine the epidemiological association between sudden deterioration leading to death and Tamiflu use.
DESIGN: Proportional mortality study.
SETTING: Japan.
PARTICIPANTS: 162 deaths without deterioration before the first consultation among all 198 deaths of mostly confirmed 2009A/H1N1 influenza. POPULATION AT RISK: Age-specific population of influenza patients prescribed Tamiflu and Relenza.
MAIN OUTCOME MEASURE: Age-stratified pooled odds ratio (OR) for early (within 12 hours) deterioration and overall death of Tamiflu prescribed to Relenza prescribed patients.

RESULTS: Of 119 deaths after Tamiflu was prescribed, 38 deteriorated within 12 hours (28 within 6 hours), while of 15 deaths after Relenza, none deteriorated within 12 hours. Pooled OR for early deterioration and overall death were 5.88 (95% CI: 1.30 to 26.6, p = 0.014) and 1.91 (p = 0.031) respectively. Baseline characteristics including risk factors did not contribute to early deterioration after Tamiflu use.

CONCLUSIONS: These data suggest Tamiflu use could induce sudden deterioration leading to death especially within 12 hours of prescription. These findings are consistent with sudden deaths observed in a series of animal toxicity studies, several reported case series and the results of prospective cohort studies. From "the precautionary principle" the potential harm of Tamiflu should be taken into account and further detailed studies should be conducted.

www.ncbi.nlm.nih.gov/m/pubmed/22156085/

Maybe not worth it for only a 12 hour reduction in flu symptoms?