Ignore, ignore, ignore when she jumps up. If you give her ANY type of response, it will just reinforce. When you become boring, and she stops, that's the exact time to praise.
Praise good behavior, ignore the bad behavior.
If she jumps up, turn around, nose to the air, arms folded. Yes, you will be spinning in circles and it will be rough for you, and she may even try harder, jump harder, add some swirling jumps, anything to get your attention, but don't give her any attention until "all four on the floor"! As soon as she is down, praise like heck! She will get it eventually. But she is 2-1/2 and has had 2-1/2 yrs of practice doing what she knows gets her attention. Take away the attention and she will eventually figure out that jumping up means being ignored.
When you praise for her being "four on the floor" that's a great time to treat with a toss of a ball or toy (her being on a long lead). Then when she's gotten it, call her back with the "come" command. If she jumps up, ignore until "four on the floor"......then toss again! It's a multi-tasking training session with ample opps of praising. And ALWAYS praise for good behaviors - ignore the bad. Boxers want to please us....so she will get it.