Ah, that makes more sense. A vet check might still be a good idea but there are a couple of things I'd suggest.
First, I hate pads for puppies anyway, they give confusing mixed messages about whether indoor toileting is allowed or not. So the issue may have started when she was in her previous home.
I'd also advise against bells, dogs often learn they are for being allowed out, as opposed to being let out for toileting. So again, a slightly mixed message.
I'm sure you know this but to cover all bases, toilet training happens when two things come together - the ABILITY to hold the toilet, along with the DESIRE to hold it in order to earn the reward for doing so.
Ideally you want her to not be in a position where she needs to toilet before you have her outdoors, so that every toilet is outside. So set her up to succeed by taking her out (not waiting for her to ask) even more than she needs; for example every 45 minutes to an hour and always after sleeping, eating, playing.
When she toilets outdoors make a huge fuss (never mind the neighbours, act like outdoor toileting is the best thing you have ever seen) and reward her with a high value treat. Do that immediately, don't make her come to you for the treat so she is clear that it's for toileting and not for coming to you. The idea is that she wants to earn the treat enough to hold the toilet until she is outside - provided there is no UTI and she is physically able to control her toileting obviously.
As she is actually performing the toilet you can introduce words she can associate with it (like 'do weewee' and 'busy busy') that later when she is reliably trained you can use these to tell her when you want her to toilet.
If you take her out and she doesn't toilet after five minutes, bring her in but don't take your eyes off her. Any hint of a toilet inside, scoop her up and get her out fast. If she doesn't try to toilet indoors (great!) take her out a second time and repeat until you do get outside toilets. You need the outside toilet to happen SO that you can reward SO that she learns.
If she has an accident inside don't react at all. If you get annoyed she may learn to fear your reaction and avoid you if she needs to toilet - the opposite of what you want. Dogs cant make the distinction between you being annoyed at them TOILETING, as opposed to toileting INDOORS. Take a rolled up newspaper and hit yourself over the head for not having taken her outside in time. Not when she is there though in case you scare her. Then clean the area with an enzymatic cleaner to remove any trace of smell that might attract her back to the spot. Indoors if you see her circling or scratching the floor, that can sometimes precede toileting so get her out fast.
Overnight she is unlikely to be able to control her toilet as her little bladder and bowel are underdeveloped and not strong enough to hold all night so set your alarm to take her out at least once if not twice during the night.
