First, the target of a Grand Jury investigation is not always called to testify before the grand jury. If they are, they can invoke their fifth amendment rights but grand jury witnesses are not allowed to have a lawyer present in the grand jury room when they testify. If the government opts to proceed without calling the target to testify -- which is what I would expect to be the case with respect to Carroll, she could demand to testify but only if she gives up her right to invoke the fifth amendment.
From what I've read, the focus of the perjury allegation relates to an October 2022 deposition in which Carroll testified that to the best of her knowledge, her legal fees were not being paid by a third person. It was subsequently disclosed that a non-profit established by Reid Hoffman was providing funding that was being used to pay for some of Carroll's litigation costs, however the details regarding the funding and whether and/or when Carroll became aware of the funding is unclear or in dispute.
In any event, it is a very slim reed on which to hang a perjury charge, particularly since the trial court held a hearing about the funding issue and Carroll was not charged with perjury at that time. Keep in mind that to convict someone of perjury, the prosecution would have to establish that Carroll made a false statement, that it was made with knowledge of its falsity and not as a result of mistake or faulty memory. Thus, even if her answer in the deposition contained "false" information, if she believed her statement to be true when it was made, no perjury conviction can be obtained. Finally, the false statement has to be "material" to the proceeding -- meaning that statement in question has "a natural tendency to influence, or is capable of influencing, the decision of the decision-making body to which it was addressed." This would be extremely hard to establish given that the trial court held a hearing on whether the fact that some of Carroll's litigation costs were being covered by a third party was relevant and concluded, apparently, that it was not.
In short, this is a completely bullshit "investigation"