Now it has been claimed the reason she pulled out of the gigs is because she is suffering from an illness called Lupus. (A spokesperson for the singer had no comment when contacted by MailOnline on Friday.)
Website Popdust reports sources close to the 21-year-old singer as saying she was diagnosed with the condition 'a couple of years ago' and that it has recently flared up again.
Lupus refers to a collection of autoimmune diseases; it causes the body's immune system to attack normal healthy cells and the impacts can be wide-ranging, effecting joints, skin, kidneys, blood cells, the heart, and lungs.
Symptoms include facial swelling, fatigue, headaches and joint pain. It can also be fatal, particularly if the it attacks the cardiovascular system.
Other celebrities with the condition include Seal, Nick Cannon and Toni Braxton - Michael Jackson also suffered with it.
One Gomez source told Popdust: 'Selena has been going full throttle the past few years and her Lupus is really catching up with her right now.
'She knows that she needs to take some time to address the disease and look after herself better if she wants to live a full and healthy life.'
Lupus is an incurable condition; sufferers commonly experience 'flares' followed by periods of remission.
It is far more prevalent in women than men and can be treated with medication to manage the flare-ups. Around 80-90 per cent of sufferers can expect to live a normal lifespan, according to the Lupus Foundation Of America
Gomez was due to visit countries including Australia, China, Japan and the Philippines on her Stars Dance tour next year, but a week ago cancelled the entire slate of shows to reflect and 'be the best person I can be'.
The full statement read: 'My fans are so important to me and I would never want to disappoint them. But it has become clear to me and those close to me that after many years of putting my work first, I need to spend some time on myself in order to be the best person I can be. To my fans, I sincerely apologize and I hope you guys know how much each and every one of you mean to me.'
The Asian leg of the tour - in support of her latest album, Stars Dance - was due to touch down in Tokyo, Japan, on January 16, followed by dates in China, Malaysia, the Philippines and Singapore.
Selena also booked five dates in Australia in February, visiting Perth, Adelaide, Melbourne, Brisbane and Sydney.
The songstress completed the US leg of her jaunt in Michigan on November 26.
She has spent Christmas relaxing with her family in California.
