Okay she needs to go back to the vet to have that wound checked out. It is possible she may need to be sedated so it can be re-sutured. What you really want to avoid is any infection in there. So my advice is pop her in to the vet (preferably the same one who did the surgery?) and ask them to take a look.
Although, if you are in any way unsure about the vet's quality of care, please take her to a new, different vet. But do it as soon as possible....today or tomorrow?
This can happen if there is a return to normal exercise too soon after surgery, or if the wound is licked too much.
YOU NEED TO RUN NOT WALK and get her into
a vet right away!!! Sutures should NOT open up
after a surgery,infection is the least thing that can
and will happen,SHE COULD DIE,so get her to
the vet who did the surgery or to someone else
who can give her the help she needs!!!!
Jan