I'd leave it! :)

Kwilter,
It would also be easier if you picked a shorter repeat.

You just need to match the centers for a square. Here's a basic no-math set of instructions (http://www.rjrfabrics.com/media/file...b8b0ba38a7.pdf).

I do use math to cut mine. The formula is

Length of side + (2 x width of border) + 1" = how long to cut strip for mitered border

So, for example, if the center of my quilt measures 65" square & I am doing a 1" border & a 3" border, I would have:

65 + (2 x [1+3]) + 1 = 74" long strips for my borders -- making sure to cut so the center of the middle repeat lines up with the center of my quilt. Yes, this method is much more wasteful.

Then, I'd seam together my borders, press them & then line up the centers & sew to the edge of the center piece, mark your 45 degree lines, and line up the marked lines. You sew right on the line & trim the excess down to 1/4". They are stunning, but require much precision/attention to detail.

Thank you all for your input, and the instructional links! Am I right in thinking that if I wanted to match up as a mitered corner, I would have to have the print cut the same way all the way around? That is, cut it all on the length of fabric, rather than the sides on the length and the top and bottom across the width?

Yes. Cut it all the same way -- either all lengthwise or all crosswise -- making sure to measure from the center out to right edge & center out to left edge, not from edge to edge.
Also, I re-discovered this Jinny Beyer video about how to do rectangles. She pieces it together in the middle so you supposedly don't have to make the repeat fit. I saw it after the last time I did a patterned border so I don't know how it works. I do wonder whether it would work with a larger repeat, but might be worth a try:
https://www.youtube.com/watch?v=cNPOkcyrMSg

I would leave it.

[QUOTE=Dina;7535521]I would just leave it alone. I like your quilt! It looks good. Look at your quilt, without looking just at the corners. See. It looks okay.

I agree. First thing I looked at was the overall colors and pattern. Then when you mentioned the third border, I admired how you matched and centered the design within the border and matched it going horizontally and vertically. I wouldn't have even noticed the corners if you hadn't mentioned it. I would leave it alone but follow the recommendations you got here for mitering the next time. Nice quilt!

Thank you for all the encouraging comments! I will leave it as is. Now I know what I should have done, and next time I can do it right.

I think you are being too hard on yourself. It looks great and once quilted even you won't notice the corner I love all the pink and it looks fantastic with your flower picture on the wall.

I looked at your quilt a while and asked myself - what's wrong with I it then saw what you were referring to with the close-up of the corner. Unless the quilt is going to be judged, I would just leave it. It's fine.