Should I be concerned over my wife's relationship with her friend?

So we've been married for almost 14 years, and in January my wife went into a business partnership with a woman about 5 years younger than her. She has a long-term bf, and we all get on well. Recently I've noticed my wife is acting a little suspiciously, however. She got a new phone a month or so ago because it was the same as her friends, and she has a code lock on it she hasn't told me. This wouldn't be unusual except she's never done that before (her old phone didn't), and said we should be able to trust each other with not knowing. She also seems nervous of when I ask to look at her new phone, and doesn't leave it with me, and watches what I'm doing with it until I've done, then takes it back. She also seems to be spending longer doing little things, like walking the dog or other tasks that take her out of the house. All little things, but enough and long enough to notice. I got a chance to look at her messages (for which I feel bad, but was hoping to put my fears to rest), and the conversations between them were talking about how "they had something very special" with smileys and lots of xxx's, and finished with "love you" etc. Nothing concrete, and they are like that together, but she's never really been like that with any girlfriends I've seen her with before. One of her friends messages ended "put dnr on text if its a do not reply" which I thought was odd - why would she need to do that? Another message asked if she'd have "10 minutes after" when they were planning a business meeting and lunch - after all morning together, why would she need "10 minutes after"?? At the moment I'm not sure if I'm being stupid and paranoid or I should be concerned their relationship is more than friendship and the business.

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