Husband has been secretly planning a holiday with a female coworker

Premise : I never heard of this woman . I found many texts between them ,subtly flirty with lots of these 🥰emoji from my husband and “caring “ phrases ,in these conversation I was never mentioned . When she asked him what he did for new years he simply replied he watched fireworks like grandpa ,nothing special . He didn’t mention what WE did after that . Anyhoo ,amongst these many texts exchanges I found some where they were planning a holiday to Egypt together with her friend and his two best friends . He denies it but then confessed they went on holiday together (her +her friend and 2 of his male friends ) in April while I was gone and thought he just went there to see his family and friends . I want to confront her and ask her some questions in regards of how many times they frequented each other . He seems to think that because he tags a lot a male friend or two it’s not a real date . I’m very hurt by my findings and obsessing over this . Would you all consider this cheating ?should I call her ?