Is Reba McEntire hearing wedding bells? According to a source, the country crooner is itching to tie the knot with boyfriend Rex Linn — partly because of ex-husband Narvel Blackstock’s April wedding to her old friend Laura Stroud. “That’s what’s really egging her on,” the confidante spilled to a magazine. “Reba’s tried to put a brave face on, but it’s got to hurt.” The source noted the mom-of-one, 69, “feels she’s met her true soulmate in Rex.” Never miss a story — sign up for the OK! newsletter to stay up-to-date on the best of what OK! has to offer. It’s gossip too good to wait for! McEntire…