All's quiet on the Shannen Doherty front. Since returning to work in January, the tempestuous star of Beverly Hills, 90210 has been ''a total angel,'' says a source on the set. ''She's been on time, hasn't thrown tantrums, and has even let the makeup artists do her face.'' Moreover, her costars have gone from vilifying her (as Gabrielle Carteris did when she was quoted as saying, ''What goes around, comes around'') to speaking on her behalf. ''I'm saddened by the whole situation,'' says Luke Perry. Could all of this mean a reconciliation is in the air? ''Not that I know of,'' says producer Aaron Spelling, who conceded Doherty has been acting ''terrific.'' (Spelling denied reports that Drew Barrymore would be joining 90210 and refused to discuss a reported meeting with Alyssa Milano.) Meanwhile, a spokesman for Doherty hints that she's anxious to kiss and make up. ''If she came back next season she'd enjoy it.''