Please take her today.

Sometimes with an older cat (any cat I guess) time makes a huge difference in the outcome, they can go downhill very quickly.

It could be something totally treatable and waiting could hamper that.

My first cat lived to the ripe old age of 19 through three bouts of cancer in his lifetime.

I feel your pain because at that age, I had no other options, but you wont know until you get aggressive and find out...and she may have A LOT more time left.

My thoughts and prayers are with you and gigi.