She is very young still, so plenty of time.
They just need watching constantly for the 'signs' that they need to go, then taking out with you so that when they go, you can praise.
Take mine out regularly during day and evening ..... every hour at least. I work from home and so could do this easily but not so easy if you are out at work in the day and training will probably take a little longer.
Do you pop pup in a crate when not supervised? We crated our lab at night and only ever had one night time accident! Never used a crate in the past but do think it helped with training. She is 18 months now and still sleeps in there at night .... seems to like it.

Would use again.
Re. your older dog .... sure it doesn't help. Can only think that you might use a fairly fragrant solution to clean up and hence help to hide the smell that might encourage pup to go indoors. Having had a dog with an old age urinary problem, I'm guessing you do anyway!
Good luck .... at least you have the good weather for those constant trips outdoors.
