Thank you for reaching out to us.
We are sorry to hear of serious marital problems.
Even when a couple is experiencing long-term problems and will not be sexually intimate, we encourage the woman to continue to immerse in the mikveh. The bracha is valid as long as it accompanies immersion, so there is no concern of a beracha levatalah.
Facilitating even casual or friendly touch can be important in improving the atmosphere between the couple, even if it does not lead to more intimate touch or resolve the couple's problems.
We have also had multiple experiences of women who thought divorce was imminent and had not immersed suddenly having a moment when intimacy seemed important. It can be important not to totally cut off that possibility.
We hope this helps. If you haven't yet, we also encourage you to seek counseling. Even when a couple winds up choosing to separate, counseling can help them do so in a more constructive and sensitive manner.
Please let us know if we can be of further assistance.