We consider the first letters of the 12 months of the year when spelled out. Thus, the distinct
first letters are J, F, M, A, M, J, J, A, S, O, N, D.......(series i)

Now, the distinct capital leers inclusive of the problem text, giving the name and dsescription
of the individual "Jason" are J, A, S, O, N, D, J, F, M, A, M ......(series ii)

Comparing  series (i) and series (ii), we observe that the series (ii) is short of one letter that is J.

Now J can denote the month January, June or July.

The only month amongst these three that also corresponds to the name of a lady is "June", and accordingly, the name of jason's girlfriend is June.