EXCLUSIVE

The ex-NFL cheerleader who allegedly tried to perform oral sex on a 12-year-old boy back in February was finally sentenced ... and TMZ Sports has learned she's NOT going to prison.

Elizabeth Garner -- who cheered for the Tennessee Titans until 2009 -- was arrested in Tennessee back in March for allegedly following the 12-year-old to a bathroom during a party in February hosted by the boy's mother.

Garner allegedly then grabbed the boy's penis over his shorts ... and attempted to remove them in order to perform oral sex on him. According to police, the boy said Garner asked if he'd ever been with a woman. Garner later told police she thought the boy was someone else (a grown man).

Garner -- who is married -- was subsequently charged with aggravated sexual battery and solicitation of a minor for rape of a child, but those charges were reduced to a single felony charge of reckless endangerment.

Now, TMZ Sports has learned Garner pled no contest back in October and was sentenced to 18 months probation, during which she must stay away from the boy and his family. She also has to submit to drug testing and attend AA sessions twice a week.

If Garner keeps her nose clean, the D.A. tells us her case will be expunged.