Hilda Pemberton, a 42-year-old former personnel administrator with the Prince George's Hospital Commission, said she was surprised when Democratic Party regulars tapped her as a good candidate for the 7th District seat she now holds on the County Council. She also had a few worries.

"I ran with the party . . . , with the ticket, I guess. I had some concerns," Pemberton said.

"But I trusted the people who were advising me and felt they knew best. I was a neophyte," she said in a soft voice during an interview.

It didn't take long for those concerns to catch up with the newcomer. Two weeks ago Pemberton decided in favor of a controversial abstention that effectively killed a council resolution to shift the alignment of the Metro Green line from a terminus at Rosecroft Raceway in Oxon Hill to Branch Avenue near Silver Hill Road in Suitland. The phone stopped ringing last week, but the political fallout may last for quite some time, Pemberton said.

Rosecroft Raceway, which would profit by subway service, is represented by Peter Francis O'Malley, reputed to be the linchpin of the once-powerful Democratic organization when the all-Democratic council voted to send the line to Rosecroft in 1978. Critics of Pemberton's abstention say that her loyalty to the Democrats who backed her overrode the interest of her own district.

"She's committed political suicide in my opinion," said Maryland Secretary of State Lorraine Sheehan, a leader of the fight to place the Metro line at Branch Avenue. "She told people during the campaign that she preferred Branch Avenue. She didn't say she would vote for it, but, whether it was intentional or not, she deceived people."

Sheehan and State Del. Albert P. Wynn, whose district overlaps Pemberton's, lost no time in launching a poster campaign in the district, placing the blame for "who lost the Metro line" squarely on Pemberton's shoulders.

A Metro line to Branch Avenue would place two rapid rail stations entirely within Pemberton's 70 percent black district. A line to Rosecroft not only would leave her district with no stations, but current Rosecroft plans call for an elevated section of track to run through a predominantly black subdivision in Hillcrest Heights, also in her district.

Pemberton said she supports the Branch Avenue line but would not vote for it until pending litigation against Metro by Branch Avenue supporters is disposed of in a Baltimore federal court. She said that if the council had voted to move the line to Branch Avenue, suits by the Rosecroft supporters would have tied up construction of the line--which has been disputed in court since 1978--until the turn of the century. Pemberton said that whenever hearings set to begin in September are over she will vote for Branch Avenue when the issue comes before the council again.

Nevertheless, Pemberton said, she realizes that her decision may never be appreciated by her constituents.

"I understood when I took this job that I was not going to be forever loved," she said.

It is the fifth job that the business graduate of North Carolina Central University has had in 12 years. In 1971 she was a psychiatric social worker in Brooklyn, N.Y., far from her native Durham, N.C., and without a degree in psychiatric studies.

"I just fell into it," Pemberton said. But that year she was laid off and her marriage broke up at the same time. She moved with her two children to the Washington area, in part because she heard there were jobs here.

"I didn't want to bring my children up in New York and I didn't want to go back to North Carolina. This was a happy medium," Pemberton said.

In short order she was employed as a supervisor and then deputy director for employe development with the county-run, federally funded Model Cities Program. Most recently she was director of personnel for the county hospital commission.

"I have a lot of confidence in myself--and a lot of skills," Pemberton said by way of explaining her success in Prince George's. Her best skills, which she says are communication and the ability to deal with people, must serve her in good stead in the Metro controversy because, she said, "I certainly don't think it's dead." As for her political skills, Pemberton said with a smile, "I'm still learning."