Usually the dark gravid spot near their vent/anus becomes darker, but I don't see the spot at all so that's not a lot of help lol. She will usually chase males away more soon and find a quiet safe spot when she is really ready. Her vent might looked popped out a bit, a tube might trail from her vent and her belly might become more squared shortly before she is ready. These don't always happen but are signs to look for. Like fishorama said though they will eat the fry. If you don't plan to move her to a birthing tank or box, add floating plants or decor for the fry to hide in. Supposedly they head for the surface, mine didn't though.