How can one repent from sins and consistently pray while continuing a love relationship that prevents them from leaving it, especially after she attempted suicide when he tried to leave her, bearing in mind that the relationship does not involve obscene or indecent language?

If you are able to marry the girl and she is permissible for you, then proceed with marrying her, as the Prophet, peace and blessings be upon him, said: "We have not seen for two who love one another anything like marriage." If you are unable to marry her, then you must sever the relationship with her, because speaking with a non-mahram young woman without necessity is a cause of temptation and a gateway to corruption. Your fear that she might commit suicide does not permit you to continue in a forbidden relationship. Rather, you must explain the ruling of Islamic law to her, advise her to repent, then leave her and occupy yourself with reforming yourself and drawing closer to Allah.