Reading someone's texts without their consent is a violation of their privacy and is not an appropriate or ethical course of action.
If you suspect that your girlfriend is cheating on you or if you have concerns about your relationship, the best approach is to have an open and honest conversation with her. Communication is crucial in any relationship, and discussing your feelings and concerns can help you both understand each other's perspectives and work towards finding a resolution.
If you feel that trust has been broken and the relationship is suffering, it's important to address those issues directly rather than resorting to intrusive measures. If you're unable to resolve the problems together, you might consider seeking the help of a couples' therapist or counselor to facilitate communication and work through your issues in a constructive manner.
Remember, a healthy relationship is built on trust, communication, and mutual respect. Violating someone's privacy can cause irreparable damage to the trust between you and your partner, and it's not a sustainable solution for addressing relationship problems.