Any advice you can give would be greatly appreciated!
If your friend is worried about her relationship, the best thing is to talk with her in person and not try to "diagnose" everything from a tarot spread. Listen and be supportive, but try not to jump to conclusions without other evidence. She could bring up her concerns with her partner and ask open, non-accusatory questions to get some clarity. If the partner seems shady, she can look into other ways to verify things - like checking message timestamps or phone records, or hiring a private investigator if it comes to that. Make decisions based on what she can confirm, and ideally the couple should work together to find a resolution.