Given that her stated goal is to win the Olympic Marathon, that is the primary Olympic 'chance' to assess.
I believe her chances of doing that are slim, less than .01%
Yes the Olympic Marathon is unpredictable. Yes many of the top marathoners do not compete in the Olympic Marathon as they chase prize money instead. (She seems more motivated by Olympic Marathon gold than Triathlon money... which is a plus for her).
But the level of talent in women's marathoning is expanding and the depth near the top increasing. Olympic gold is a big enough prize that there will be many 2:20-2:24 runners there waiting for any sub 2:20 runners to fade. Even if she gets fast enough to be at that level, she will have lots of company.
In 2017 , 48 women broke 2:25 for the marathon. 22 Ethiopinans, 19 Kenyans, 3 from Japan, 2 from Burundi, one from Mexico and one from the USA. The odds of one of the 6 Kenyans and Ethiopians at the 2020 Olympics winning gold will be high.
Running is much deeper and more competitive than triathlons. Many of the best marathoners come from the African continent, and how big are triathlons in Africa?
The Olympics will be in Japan, and there will be 3 Japanese women willing to die for the win. I believe 30% chance of a Japanese woman getting a medal.
I don't believe making the 5 or 10k team interests her. That is not her goal. Also, I think she realizes that the chance of her winning the Olympic 5 or 10k are much less than winning the Olympic Marathon. Too many fast people in those races and the fastest 5-10k runners in the world do show up to run the 5 and 10k at the Olympics. Those events are more predictable than the marathon.