Hello HB,
She will probably come back. You have been enabling her addiction, and you will continue to do so unless you get some serious help for your codependency, so, yes, she will likely come back. She knows how to manipulate you, she knows you will rescue her, she knows you are an easy mark.
People who enable drug addicts do them no favors, impede their chance for recovery, and often bring the chaos of their relationship with the addict into the lives of their friends and their family members.
"Relapse" is not the right word. She is not in recovery. She has never been in recovery. She doesn't relapse. She simply pauses between using.
There is no "turning a corner" in the situation as it is today. You enable, she drugs, and the merry go round keeps on spinning.
You can't control her using, though it seems from your post you think you might be able to do just that. But you can contribute to it by constantly rescuing her from the normal and inevitable consequences of her addiction.
Find yourself a counselor or a Nar-Anon group, start your own recovery, and become thoroughly educated about codependent behavior. You, I am sorry to say, are not what she needs in her life unless you yourself get well. . Best of luck to you, and I hope you both find recovery.