I think your mentor has gone into the quilt police area with her rules. Our grandmothers made wonderful quilts with any old treadle they could get their hands on so ditch the advice about getting a new(er) machine unless you feel the need. Borders do not need to be scary. Lay your quilt top out flat on a table or the floor. Measure through the center of the quilt lengthwise and cut your borders to that measurement. Fold the quilt top and the borders in fourths and pin at each fourth and also in between if you wish. Sew them on. Then lay your top out and measure through the center of the top again widthwise including the borders you just sewed on. Again measure the quilt and the borders in fourths and pin them on, adding pins as needed. Sew them on. When you sew the borders on lay your border fabric on top of the quilt top. It makes it much less likely to stretch and give you wavy borders. Not as difficult as your "mentor" made it sound. Good luckj!