What happens ultimately is that either you
communicate this problem to her and make it a 'known issue', or you
simply wait for a sudden implosion to occur before you direct this
force outwardly and create devastation.
You must also remember, it is precisely this nature of her that
probably allows you to get close to her without much difficulty.
Surely, other guys would have done the same thing and forge the
same bonds like the way you do - the only difference is that either
you made more impact or you were 'faster' in your approach, in
which love has developed.
Kinda obvious about this guy's intention to advance on her -
jealousy only occurs when feelings are invested and if he is
feeling it, he's probably investing chance, time, money and
emotions? And likely, he could seize opportunity to give your
relationship a low blow, especially when there are frictions
brewing from conflicts?
This is the dilemma of leading relationship: should we sacrifice
short term, in which our relationship will benefit a broader frame
of time, or are we to sacrifice long term to appease short term
gains?
You worried about communicating serious and unpleasant issues to
your partner, in which a bulk of your worries comes from the fear
of losing this relationship. You may decide to keep mum because you
would choose to ignore your own concern by brushing it away, but
certainly, you wouldn't be able to put it aside for long before you
start trashing things. This is sacrificing long term to appease
short term gains because once she get 'used' to you behaving in
that manner over a long period of time, it would be difficult to
make major adjustment in your relationship later or the cost of
implementing those changes will be tremendously pricy.
You may like to let her know, over a causal dinner, that this guy
is questionable, although you have no plans to restrict her in any
sense and you still allow her the freedom.
In the long run, the key is to resolve her insensitivity - not the
man around her.
P.S: In marketing, generating awareness does not always equate to
sales. But company are still doing it because they see it as a
necessary evil? 
Cheers
