Are you referring to Teabag? The chances are she will already be speyed, but thats no guarantee. I would wait, personally, to see if she shows any sign of season, or get her flank shaved to search for a suspicious scar. The only way to tell 100% whether she IS speyed would be to open her up, which we have done before. Even a scar could be from something else.
If you were to get her opened up or you know she is entire and need to get her done, make sure you get a pre-op bloodscreen done first to check that all is okay. We always offer bloodsceens to every animal over the age of 8 coming in for surgery. If all is well on bloods, we have done plenty of surgery on very old animals without problem.