Alternate timeline
(covers information from an alternate timeline)

Jessel was Data's housekeeper with a British accent in an unknown, alternate future timeframe, when he was a Lucasian Chair professor at Cambridge University.

Data noted that although she was "trying at times" (when she likened the new style of his hair to that of a "bloody skunk," for example), she made him laugh.

She had her tea preparing skills questioned, bordering on insulted, by Jean-Luc Picard when he stated her Earl Grey tasted like Darjeeling.

After agreeing to help Picard figure out his dilemma, Data asked Jessel to have Professor Rippert take over his lectures for at least tomorrow, and possibly for the rest of the week. (TNG: "All Good Things...")

Jessel was played by Pamela Kosh.
In the script, Jessel was described as an "...English housekeeper..." and as "...a dour woman in her fifties with a heavy British accent." [1]