She played the field all summer, but Drew Barrymore may be falling in love this fall.

The star, 32, continues to rev up her romance with her He’s Just Not That Into You costar Justin Long, 29. The duo, first linked in August, enjoyed a weekendlong PDA-fest at the Austin City Limits Music Festival in Texas, where “they were making out all over the place,” says a source.

On September 15, they smooched through a bash for Arcade Fire at the Belvedere Music Lounge; the next night, they got cozy at a Wilco show. “They were like kids in love,” an onlooker tells Us.

Back on the L.A. set of their comedy where they have yet to share a scene, Barrymore texts Long during breaks.

Says a source, “She’s really into him.” (Of course, just months ago she seemed really into director Spike Jonze, 37, “but she was never monogamous,” says a pal.)

With Long? “You can definitely tell that she likes him!”

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