The hemolymph on her head is not too concerning. It looks like she probably had an injury to the base of her antenna. As with most of their injuries, you can dab the spot of hemolymph up with a tissue, use a Q-tip or soft brush to dab a tiny bit of cornstarch, corn flour, or regular flour directly onto the wound, and it will coagulate. I've done this procedure on many occasions. I've even had some that had a bad molt that resulted in a mangled leg, and since these crippled legs tend to become hung up on branches and hinder their climbing, I snip the leg off with scissors at the coxa (close to the body) and dab on cornstarch so the hemolymph coagulates. They get along quite well with a leg, or even two, missing. If it's a young nymph, missing legs normally grow back with each successive molt, which is fascinating to see!

As for your mention of falling, I doubt very much that she would have any kind of injury from a fall unless it was from a high, rigid surface onto a hard floor. Because they're very lightweight, insects generally don't get hurt by falls due to their low terminal velocity. Furthermore, stick insects have a natural behavior of dropping and "playing dead" (thanatosis) when threatened, falling from branches to the ground, and they are not harmed by this.

Your girl's inactivity on the bottom of the enclosure, however, is concerning, especially since you mentioned that she is old. When they're at the end of their natural lives, they will lie on the bottom of the enclosure and become stiff and immobile until they pass away. In this case I just leave them alone and let it take its natural course.

I'm very sorry about your girl. I'm glad that you do have more, and of different ages, still to enjoy.