The first person to suspect Claus C. von Bulow of trying to kill his heiress wife today admitted there were discrepancies in what she told a grand jury and what she has said in von Bulow's trial.

Maria Schrallhammer, personal maid to Martha (Sunny) von Bu low for 23 years, said she had not revealed to the grand jury the reason her mistress contemplated divorce because she had promised to keep it in confidence.

"I just wanted to protect my lady if she came out of the coma, and I hoped she would," Schrallhammer, 59, said in her third day of Superior Court testimony. "I was still hoping she would come out of the coma and I didn't want to betray her."

In contrast to what she told the grand jury, Schrallhammer last week testified that Sunny von Bulow said she wanted a divorce because her husband was unhappy and blamed her for not being able to find a job.

Under cross examination by defense attorney Herald P. Fahringer, Schrallhammer also acknowledged she told a grand jury she was surprised but not concerned the first time she found insulin in a black bag among von Bulow's belongings a month before Sunny von Bulow fell into a coma, from which she is not expected to recover, in December 1980.

But in court, Schrallhammer said, "I asked Alexander von Auersperg, von Bulow's stepson 'What for -- insulin?' because Mrs. von Bulow has hypoglycemia and doesn't need insulin."

The German-born maid is a key prosecution witness in von Bulow's trial on two counts of attempted murder. She testified last week during two days on the stand that she secretly gathered evidence in the financial consultant's New York City apartment and Newport estate.

Following Schrallhammer's testimony, the cook who worked for Sunny von Bulow when the heiress was "in residence" at Clarendon Court with her family testified that before her mistress went into a coma on Dec. 29, 1979, Schrallhammer "evidently had been prevented" from going into Sunny von Bulow's bedroom by Claus von Bu low.

The testimony from Irene Silvia, who worked for the wealthy family for eight years here, corroborated the damaging testimony from Schrallhammer, who told the jury that while her mistress was "moaning" and "unconscious" that day, she had gone into the bedroom against the orders of "the mister" -- referring to von Bu low -- and had tried for hours to make him call a doctor.

Other domestic employes from Clarendon Court, where von Bu low allegedly made two attempts on his wife's life during Christmas visits in 1979 and 1980, are due to be called to testify in Superior Court this week by prosecutor Stephen R. Famiglietti.