Sources close to the family tell TMZ ... Tameka has not lost hope that her son, Kyle Glover, can make a drastic recovery ... despite doctors declaring him brain dead last week following a jet ski accident. We're told she is telling friends ... she still believes in miracles.
According to our sources, Tameka can only keep Kyle on life-support as long as her insurance company agrees to pay ... otherwise she doesn't have the funds to cover the enormous hospital bills.
We're told the insurance company hasn't set a specific deadline, but they've made it clear ... they're only willing to shell out coverage for a couple months ... tops.
Our sources say that Usher -- who helped raise Kyle for several years -- has been incredibly supportive in this difficult time... but has NOT offered to pay for any medical bills. We're told Tameka does not see him as a viable financial option.
As TMZ first reported, Kyle was struck in the head by a jet ski while inner tubing on Lake Lanier -- doctors declared him brain dead days later.