"If you’re reading this it means I have died, I made it 5 & half years though, not bad for a stage 4 breastie ey [sic]," she wrote in an Instagram post shared with her near-300,000 followers after her death.
Newman, from Surrey had created a following thanks to her "go grab life" attitude after her stage four breast cancer diagnosis.
"Nick. I love you. So grateful I got to meet and know you. Promise to grab life every single day," Stacey Solomon commented on the post.
Giovanna Fletcher added: "You have inspired so many to go and grab life, just as you did whenever possible. Sending so much love to your loved ones."
Strictly Come Dancing's Amy Dowden, who was diagnosed with breast cancer earlier this year, also paid tribute to Newman calling the campaigner a "beautiful ray of sunshine".
"[Newman] has done so much and created a community and legacy that will live on," Dowden added.
Dowden was diagnosed after she made a conscious effort to check her breasts following a fundraising walk she did with charity CoppaFeel! last year.
Read more: Strictly's Amy Dowden pays tribute to late friend and breast cancer campaigner (Digital Spy, 2-min read)
"CoppaFeel! has now potentially saved my life, because I don't know how long this lump could have been there before I would have noticed and done something about it," the professional dancer, 33, told Hello! magazine earlier this year. "So me speaking out might end up saving some other people's lives because they start checking their breasts."
How to check your breasts
We all have breast tissue, so all genders should be checking theirs once a month, whether that's in the shower, in bed, or before getting dressed.
While you can follow it in the order that suits you, CoppaFeel! has put together the three most important breast-checking steps.
Look at your boobs
Look at the area from your armpit, across and beneath your boobs, and up to your collarbone
Be aware of any changes in size, outline or shape and changes in skin, like puckering or dimpling
You may find it easier to use a mirror, and if you can, look with your arms both raised and down by your sides.
Feel each of your boobs
Feel the area from your armpit, across and beneath your boobs, and up to your collarbone
Be aware of any changes in skin like puckering or dimpling, or any lumps, bumps or skin thickening that are different from the opposite side
If you can, you might find it easier to feel with your arms both raised and down by your sides, or lying down
Watch: Linda Evangelista was diagnosed with breast cancer twice in five years
3. Notice your nipples
Look at each of your nipples
Be aware of any nipple discharge that's not milky, bleeding, rash or crusting that doesn't heal easily and change changes in the position of your nipple
Again, you may find it easier to use a mirror.
Remember that when looking and feeling, you should repeat each step for each side of your breasts.
When to get help
It's important to become familiar with what's normal for you as everyone's breasts are different, so you can identify any changes more easily. Plus, remember, it's also normal for them to feel more tender and lumpy when on your period, softer when you're post-menopause, or to have one larger than the other.
To familiarise yourself further about what might not be normal, see our useful guide on breast cancer signs and symptoms.
If you notice anything that doesn't feel normal, monitor it for a week, and book an appointment with your doctor.
If in doubt, get it checked out.
For support, you can also call Breast Cancer Now's free helpline on 0808 800 6000.
Breast cancer: Read more
Breast cancer symptoms as survivor Sarah Beeny says she feels 'very fortunate (Yahoo Life UK, 6-min read)
How to book a mammogram as Susanna Reid details 'hurdles' in securing an appointment (Yahoo Life UK, 4-min read)
Sarah Beeny and other celebrities who have shared their breast cancer journey (Yahoo Life UK, 7-min read)