Am I right ??

If it looks like a duck, walks like a duck and quacks like a duck" it's a duck, so yes she's seeing someone else by everything you've described, but because she's refused your offer of sharing, that tells me she's probably having an affair and has no interest in being shared as such.
I'd say she has a lover in the true meaning of the word.
Yes looking like it - just she’s so fuckin slippery and want to catch her out at it be cause she so comes across as this richeous prude where I’m a fiery bastard for even suggesting a half decent sex life while she’s out getting pumped looks like and has done before a few times with other partners - I know for a fact she cheated on her last partner even though as per usual it’s deny deny deny / gaslight and turn it back round on me . The double standards and narcissism from her is off the chart
 
Is her ...... from the ex husband? Do you have any interaction with her? Do you know anything about what the ......'s attitude is towards her father?
Ah that’s cool coastal kid I get the gist - yes she is from the ex and she used to live with us until recently and gave me lots of hassle being overweight , spoiled , entitled etc etc . At one point an ex of the wife had messaged the step ...... on Facebook and asked if it was ok that he was in contact with my wife and she said - yes I’m fine with it - that was my biggest mistake - should have kicked both of them out there and then but it was turned back to me - how dare I record them , illegal etc etc . My wife was in communication with him and the stepdaughter was fine with it - nothing about you shouldn’t be talking to my mum behind her husbands back as truth be told she didn’t like me one bit because from day one I treated her like an adult and didn’t feel sorry for her that - she was way overweight - didn’t / couldn’t get a boyfriend / didn’t have a social life / no friends apart from a gay man - you couldn’t fucking make it up . . I still have the recording and it is very damming on her part but invaluable for me . Which is why I think she is back in touch with this same guy - she told me - he was ‘the one ‘ so determined this time to get concrete evidence that she can’t gaslight or squirm out of . Tonight she got a ping or what I’d take to be maybe a WhatsApp message - as I was sitting next to her !! . Needless to say she didn’t attempt to answer it ,