I would put her on leash, go outside, tell her “go potty.” She does something. You praise you let her off and let her have a good time or whatever she wants to do. If she doesn’t do anything, you go back inside for 2 minutes, then walk back outside. Say “go potty” and repeat the process until she does something.
You’ll have to figure out her schedule though. Not sure if my dogs are on my schedule, or it just fits my life, but they go in the morning and then in the afternoon after work. It’s about a 12 hour cycle give or take. So since she’s older, I’d assume she’ll also be on some sort of cycle as well. So you should be expecting #2 at around those times when you usually see her do it. Right now…it sounds like she has to go when you’re gone, somehow you’ll need to adjust that. I think my method above will work to do that, but no guarantee.
We had a little bit of a housebreaking problem with my newest dog who came to us after living with someone who was home all day and could just let her out at all times of the day. So she didn’t really get that she should be going when she gets let out and that’s all the time she’ll get because we’re going to be gone for 8 hours during the day. Eventually, with proper management when we were home, and I think with the help of our other dog, she’s gotten on the same schedule as the rest of the house.