Doctors said she had a 20 percent chance of surviving five years if she started immediately on radiation treatment.
But knowing that this could kill her unborn children, Danielle refused, and carried her son Colby and daughter Reagan as far as she could - giving birth at 29 weeks in July, with each baby weighing just over three pounds.
Danielle was put on intensive treatment straight away, but it was too late.
On April 26, she passed away in her hospital bed in Houston, surrounded by family.
'The leptomeningeal disease spread faster than anyone was expecting,' Rachel Miller, Danielle's sister, wrote on the family's GoFundMe page.
'There was enough time that family was able to make it to Houston to spend time with her. Tyler was laying with her when she passed peacefully.
'We are all heartbroken and devastated and can't imagine a life without Danielle.'
Doctors believe Danielle's melanoma cancer was caused by a mole that was removed in 2011.
Her husband Tyler had noticed a strange mole on Danielle's back in 2010, but a dermatologist said it was benign after a biopsy and told her not to worry about it.
However, the mole grew back and still looked funny, prompting the couple to seek a second opinion.
This time, the biopsy confirmed it was melanoma and surgery was performed to rid Danielle of the cancer in late 2011.
After the operation and bi-annual checkups at the dermatologist, Danielle was considered cancer-free after five years.
She went on to conceive and delivered a healthy baby girl, Taylor, in 2015.
The small family was overjoyed when they learned Danielle was pregnant again, this time with twins in December 2016.
It wasn't until April when Danielle was 17 weeks pregnant that they learned the melanoma had returned, this time in her brain and stomach.
During pregnancy, Danielle had some operations to battle the cancer - removing three masses from her brain, two from her abdominal wall, and undergoing targeted radiation on her brain.
But she postponed the most aggressive radiation treatments, chemotherapy, and scans with contrast dye to ensure the safety of her twins.
All masses were found to be melanoma, the same cancer as the original mole that was removed.
As soon as the babies were born in July - weeks after Danielle and Tyler celebrated their ninth wedding anniversary - the doctors' first concern was checking their placentas for traces of melanoma, and both were declared negative.
Regardless, they spent weeks in the NICU regaining their strength, since they were born 11 weeks earlier than would be ideal.
They strengthened quickly, and Danielle, too, seemed to be making progress.
In September, within two months of giving birth, scans showed no new growth of her adrenal tumor.
However, it also revealed a brain lesion that may not have been there before. She was started on immunotherapy, which is the new darling treatment for aggressive cancers, particularly in the brain.
By Thanksgiving, the picture looked bleak: despite going back to work, her scans revealed more tumors in her brain.
The twins, meanwhile, continued to gain strength.
In March, Danielle's sister informed their GoFundMe well-wishers that scans showed a new tumor on her spine and more in her brain.
That meant the cancer had likely spread to her cerebrospinal fluid (CSF), which is almost always fatal as it can spread far quicker than doctors are able to track it. The only viable treatment method was to insert a catheter direct into Danielle's brain that would deliver chemotherapy drugs into her CSF.
Eventually, at the end of March, the family relocated to MD Anderson in Houston, Texas, for a one-month treatment program.
While she was there, she developed an infection.
Despite receiving a new catheter, she died a few days later.
Until the end, Danielle was pictured beaming in every photo, with her family calling her a 'fighter'.
Relatives are now rallying around Tyler and the children to support them.
Throughout, her sister has been updating Danielle's story regularly online, following Danielle's wish to warn others about the dangers of easy-to-miss cancers.
Even before giving birth, Danielle said: 'I want people to know skin cancer is not something to be brushed aside. People need to get skin checked and wear sunscreen. People think [skin cancer] is more treatable, but if it metastasizes the prognosis isn't good.'
Metastatic melanoma is the most serious case of skin cancer and is when the cancer has spread to other parts of the body.
It is the most common form of cancer for young adults and is the leading cause of cancer death in women 25-30 years old.
Melanoma is a skin cancer that begins in the melanocytes, a special type of cell. As with other cancers, this occurs when the melanoma is not caught in the early stages.
Oftentimes, symptoms only become present once it is has already spread.
The most obvious sign is a new or strange colored mole. Most melanoma tumors are brown or black, though some appear pink, tan, or even white.
Other symptoms include hardened lumps under the skin, swollen or painful lymph nodes, difficulty breathing, persistent cough, swelling near the liver and bone pain.
An estimated 90 percent of melanoma cancer is caused by exposure to UV light, which includes exposure from the sun and artificial sources, such as tanning beds.
The five-year survival rate for stage 4 melanoma is less than 20 percent and the 10-year survival rate is 10 to 15 percent.
The Cleveland Clinic last year claimed that skin cancer is more deadly for pregnant women and new mothers.
The study found women diagnosed with melanoma during pregnancy or within one year of giving birth are five times more likely to die.
Scientists said they believe hormones circulating in the body during pregnancy, namely estrogen, are responsible for the increased risk.
