No. An inmate's C-file, the central file maintained by the Department of Corrections that contains their complete institutional record, is not accessible to family members or significant others. It is confidential and protected under the same privacy framework that governs any personal record.
The only person who can formally request and review the C-file on behalf of an inmate is an attorney of record. Once an attorney is retained or appointed and appears on the case, they have the standing to request the file through proper legal channels. That record can be essential in building a defense or addressing new charges because it contains documentation of classification decisions, prior disciplinary findings, programming history, and other information that can be relevant to how a new case is handled.
If your partner is facing new charges and does not have an attorney, getting one is the most important step. Once an attorney is on the case, accessing the C-file and any relevant records becomes part of their discovery process.
What you can do from the outside is help document what you know, gather any records you personally have access to, and make sure the attorney has as complete a picture of the situation as possible from your vantage point.