Is liposuction necessary for breast reduction?

You need a formal evaluation by a licensed plastic surgeon and expert in breast reductions to determine what is best for you and your goals.
Breast reduction is one of my favorite surgeries as it allows me to dramatically improve a woman’s breast appearance as well as alleviate many physical symptoms of large breasts, such as back, neck and shoulder pain, bra strap grooving, and rashes under the breasts. When I perform breast reduction surgery, I generally use a superomedial pedicle to provide blood supply to the nipple while maintaining fullness in the upper and inner breast. Excess lower and outer breast tissue are removed. Breasts are often asymmetrical, so I remove more tissue from the larger breast. The final scar pattern is a circle around the areola, down the breast, and possibly under the breast, depending on the degree of skin excess.
For me, breast reduction is not a one-size-fits-all surgery. The size and shape of the breasts are customized to each patient depending on her goals and desires. Some women want a significant amount of tissue removed while others prefer to have a more limited reduction. Regardless of the amount of tissue removal, I perform the maximum safe amount of lifting and tightening for each patient.
I suggest consulting with a board-certified plastic surgeon and expert in Breast Reductions. - Dr. Cohen

The breast reduction can be approved by insurance, and cosmetic surgery can be combined in addition to get a break on anesthesia and facility fees.  This is not impossible and is done frequently.   Axillary breast tissue removal is difficult with liposuction alone.  The tissue, however, may be fat, which, of course, is amenable to liposuction. Perhaps you can consult with your friend's PS and compare costs, results, etc.

While liposuction is not "necessary" to perform a breast reduction, it is often recommended to improve the result in the axillary area.     Understand what the benefits are, and, if you are bothered by the area, you can always have that done later.