It could be habit. Or maybe 9 hours is too long for her at the moment or does she get anxious in the night?

Could you let her out during the night? Say at 2 o'clock?

Hello Edwina I am not a fan of training pads, they are an indication to a dog that it is ok to soil inside when this is not the behaviour you want though I appreciate you may have been using them because you were away from home.

Adult dogs should be capable of controlling their bladder overnight and during sleep the urge to urinate is suppressed.
Some spayed bitches have urinary incontinence which can be helped with medication. A vet check is recommender if you think there may be a medical problem.

You can train a dog to extent the time it can wait to urinate during the night. First you need to take the dog out as late as possible then go down early say 6am / check if it has been clean/take it out.

If it has already soiled go earlier the next night. Clean up any mess thoroughly to remove the scent (no word no eye contact with Megsy , you don't want her to associate your presence and the presence of urine with fear. )
When you have established a time she is still clean go down and take her out at that time for a couple of weeks then very slowly extend the time by a few minutes every couple of days.

ETA don't forget the praise and a high value treat (like chicken) when you take her out and she eliminates. You want to establish that waiting to go outside is a rewarding experience going inside brings no reward .