Kimberley Renicks, 27, is Britain's top-ranked player at -48kg but needs a strong run of results to leap almost 25 places into the world's top 16.
"We budgeted for £20,000 for the full year. We got £8,000 and that's all spent," said Louise of her fundraiser.
"Unfortunately, in judo there is only a small amount of funding."
The Renicks sisters, from Coatbridge, enjoyed high profiles during the 2014 Commonwealth Games in Glasgow, winning the host country's first gold medals.
However, the battle for funding, combined with recurring injuries, led 32-year-old Louise to retire from competitive judo this summer.
She now combines a part-time job as a sports development officer with coaching her younger sister and helping her realise her dream of fighting in Rio.
Louise sees part of her role as shielding Kimberley, who has returned from a shoulder injury, from the stress of finding money for flights and accommodation, with the duo using a crowd-funding website.
Money from Judo Scotland, who are allowing Louise to help with her sister's programme up until the Olympics, will cover Kimberley's costs in January but Louise feels British Judo should be doing more to help in the months that follow.
"The British trials are in two weeks' time and it will be Kimberley's last competition of the year," she said.
"Even getting the number one spot, she will be hoping British Judo can provide something.
"I know that January competitions are covered so it's February and March competitions that we need to worry about.
"Even taking the British number ones for the girls and the boys in the seven weight categories, that's 14 athletes but only eight athletes get that funding.
"Money might go to athletes in other weight categories with a slightly better record.
"[Since the Commonwealth Games] money went up in certain areas but it's not gone up so much in the elite side to give athletes a wage to be able to live and pay for competitions.
"It's still quite low there, but in the development side, the recreation side, the active side, all that has gone up in Scotland.
"It's hard to go to the Olympics and get your dream."
The sisters targeted an initial six events to boost Kimberley's ranking points, but she lost in the first round of the first two, then picked up two bronze medals before two last-16 finishes in Grands Prix.
"Out of the 500 points she needed, she came away with just over 120 so we need in the 300 mark," said Louise of her sister's Rio target.
The Renicks' travels for ranking points in the coming months will take in 12 competitions and will include destinations such as Cuba, Chile, Uruguay and Argentina, plus some in Europe.
"I'm going to the other side of the world to fight the athletes that, if I do qualify, I will come up against at the Olympics," said Kimberley. "You have to learn how to fight their style.
"It's a full-time job but you don't get paid for it. That's the hardest bit. But walking away from Rio with a medal would be a dream come true."

The application was rejected in September 2014 by Fifa's executive committee, which said its requirements had not been met.
But the Court of Arbitration for Sport has told Fifa to submit Gibraltar's application to its Congress, which has the power to grant membership.
European football's governing body Uefa accepted Gibraltar in 2013.
Fifa is now set to discuss the situation at their next Council meeting, scheduled to take place on 9-10 May.
It will decide whether to amend the agenda at the next Congress in order to submit Gibraltar's application for membership.
A 6-0 defeat by Scotland in October saw the part-timers finish bottom of Group D in Euro 2016 qualifying without collecting a point.
However, without being accepted by Fifa they will not be able to enter the World Cup qualification process.
Cas said on Monday that Fifa's Congress "shall take all necessary measures to admit the Gibraltar FA as a full member of Fifa without delay".
Louise Renicks is concerned that a lack of funding will shatter her sister Kimberley's dream of competing for Britain's judo team in the Olympics.
[NEXT_CONCEPT]
World football's governing body Fifa has been instructed to reconsider Gibraltar's application for membership.