Large Breasted Client
Hey Silver Hawk
I agree with Moogie - you should release the pecs and front delts, as well as serratus anterior and even upper abdominals; all the muscles in the front that are contracted from being pulled forward by the extra weight in the front.
First though, it would be good to try and balance out her pelvis with whatever techniques you are comfortable with. Chances are, her posterior neck muscles are tight because they are fighting against the forward-pulling to straighten out her line of sight and the front neck muscles are over stretched. If this is the case, you can balance her neck by working the post. muscles deeper and tighten up the anterior, for instance, by have her contract her neck against your resistance (make sure to support the curve/ no straight neck). The pelvic and neck work will help balance her alignment and give you better, longer-lasting results.
Just like the neck, you want to balance the front and rear of the trunk. Here, it's the posterior muscles that are overstretched so I would just do some MFR, then release any trigger points followed by some toning work to tighten them up and balance the anterior/posterior dysfunction.
What I've laid out here is part of a typical myoskeletal alignment protocol so take want you want from it and - Good Luck!