Your wife's year of birth affects her "bend points" and so my calculation might not be completely accurate but it should be close. Your story did not sound right initially and I would not want you to get a nasty surprise upon retirement. As you can see below, your figures could be correct. Congratulations.
If I use the current cap on FICA taxed earnings of $132,900 and assume your wife earned (the SSA indexed equivalent of) $132,900 for 25 years, then her list of 35 highest (SSA indexed) earning years would consist of 25 items with $132,900 and 10 items with $0. If I add these up and divide by 35 (i.e. if I average these) and divide by 12 (to get monthly averages), I get:
(1) $3,322,500
(2) $3,322,500 / 35 = $94,929
(3) $94,929 / 12 = $7911 (AIME)
Now the bend points become important and I don't know her bend points. My guess at her PIA is $2560 but her amount will be a little higher because her bend points are higher than the ones I used. So $2615 is within the realm of possibility.
If she had 35 years of earning $132,900, her AIME would be $132,900/12 or $11,075 and her PIA would be (somewhat above) $3034, let's say $3094. Since $3094-$2611 = $483, your comment "Had she kept working another 20 years from 45 to 65, her benefit would have only gone up a couple hundred a month" is correct if $483 is "a couple hundred"