Out of all the relationships Beth cultivates in The Queen's Gambit, her friendship with Jolene is the most meaningful; Jolene is the only person who can (and does) help Beth when she's at her lowest point. Beth experiences many highs and lows in her professional and personal life, but after years apart Jolene once again becomes an integral part of her life when Beth is struggling through a breakdown.
After her mother commits suicide at the start of The Queen's Gambit, Beth is sent to an orphanage, where Jolene - an older girl who hasn't been adopted out - befriends and schools her on the ways of the institution. She also warns Beth of potential addiction to the fictional tranquilizer Xanzolam, which allows Beth to hallucinate chess plays on the ceiling at night. Jolene is understandably bitter when Beth is adopted by the Wheatleys, as she comments earlier that older, Black children aren't likely to leave the orphanage. The friends lose touch until years later when Beth is battling addiction and Jolene shows up at her door to see her through.
Jolene is the only person who can help and uplift Beth because their friendship doesn't revolve around chess, but around their shared experience as orphans. So many of Beth's connections stem from her talent – even Beth's adoptive mother Alma starts to show interest when Beth wins a local tournament. Jolene knows Beth before she earns national and international acclaim, so she's more attuned to Beth the human, rather than Beth the chess player. At the orphanage Jolene is supportive of Beth's pursuit of chess, but she's more concerned when Beth shows signs of withdrawal from the tranquilizers. When they're reunited, Jolene – who has become a successful paralegal in her own right – calls Beth out on her drug and alcohol use again and advises her to stop digging herself into a hole. She also returns Beth's copy of Modern Chess Openings, which she stole out of resentment before Beth left with the Wheatleys.
The biggest contribution Jolene makes to Beth's life and career is funding her trip to Russia after Beth turns down her Christian Crusade sponsorship. Beth is shocked and calls Jolene her guardian angel, but Jolene reminds her that they weren't orphans as long as they had each other. They're essentially family, and family helps each other out without question. Jolene willingly dips into her savings for law school to help Beth out because she's kept up with Beth's career, so she knows how much this upcoming tournament means to her. She also fully expects payback when Beth wins the title of Grandmaster.
Unfortunately, viewers don't gain much insight into Jolene's character because The Queen's Gambit mostly has her exist to service Beth's narrative arc. In many ways, Jolene falls victim to the "magical" person of color trope. Though she is underdeveloped in this way, Jolene does provide unconditional love and support to Beth and opens her eyes to the majority of people who must work hard to achieve success, rather than just being gifted with it. This is why she's the only person who can put Beth back on the right track.