she flirted with someone younger that she found attractive and was reciprocating the motions.
when realizing it was something more than that and that your feelings could be hurt/affected; and her relationship severed; she backed away.
shes old enough to know the end result; and wise enough to not go down that path if she truly cares for her partner and sees/wants a long term future with them.
this is why shes backing off (even if for a moment she entertained the thought of fucking you; and tries to stay close with zero intent of furthering that; by her simply hanging around; with you both on a thread; to satisfy her own selfish pleasures; warning signs are flashing).
im sorry op; i truly dont think anything serious, nor a sexual relationship between you both; was intended to be and in the long run will only lead to trouble granted your current professional relationship with them both.
...kytnism...