Unnerve:
Ask her what she means by 'missing you' but be prepared to listen to a lot of pointless explanations, emotional blackmail, and some expert reverse psychology back at ya for going through her messages.

If you know what's good for you, get a grip on your emotions & don't react. Just take note of this and keep checking up information regarding this particular person - the frequency of their exchanged calls, the WhatsApp messages.

No woman will ever admit she is cheating on you until you catch her red-handed in the act itself, or perhaps you see a chat where she is specifically talking about having sex. Anything other than this, it's expert analysis you're just looking for, lol.

Thanks.

My head is clear now and my decision has been made.