Coming to this late and I can see the OP got sorted with the Funkey cards, but this thread comes up when you search for times tables help so I thought it was worth adding the thing that actually changed it for us, because it is not on the list yet.
Before picking any app or any method, find out which facts she is genuinely missing. Not "the 3 times table", the individual facts. Sit down with a blank grid, or just call them out in a random order, and mark the ones where she hesitates for more than a few seconds. Takes about ten minutes.
The reason it is worth doing is that the job is far, far smaller than it looks. There are 144 facts in a 12 by 12 grid, but 3 x 7 and 7 x 3 are the same fact, so really there are 78. Take out the 1s, 2s, 5s, 10s and 11s, which almost every child already has, and you are down to 28. Take out the squares, which tend to stick early because children like them, and you are left with 21 facts. That is it. Twenty-one.
And they are always the same ones. 6x7, 6x8, 6x9, 7x8, 7x9, 8x9, and the 12s. When my eldest was struggling it turned out he knew everything except about fourteen facts, and he had been carrying around the belief that he was "bad at times tables" for a year. Telling him there were fourteen things left to learn, and writing them on a bit of paper stuck to the fridge, did more for him than any app did. It stopped being a mountain.
Worth knowing too that the 6 second target people mention upthread is not arbitrary. The statutory check they do in Year 4 gives them 6 seconds per question, 25 questions pulled from the 2s to the 12s, and it deliberately asks more from the 6s, 7s, 8s, 9s and 12s. So the exam board has independently worked out where the hard bit is, which is reassuring when you are trying to decide what to prioritise.
On the actual how, I would gently push back on marching up from the 3s in order. It feels systematic but you spend three weeks on facts she already knows and arrive at the hard ones tired. Go straight at the ones she missed, five minutes a day, and revisit anything she got wrong two or three days later rather than the next day. The gap is the bit that makes it stick, which is why an app that just reshuffles the same twelve questions does not work as well as it should.
Resource-wise, Hit the Button (free, Topmarks) is genuinely the best free thing for raw speed and several people have already said so, rightly. TTRS is excellent if the school already uses it and she is engaged with it, less so if she has grown out of it, which Bunnycat101 makes a fair point about. For something that tracks which specific facts are weak and brings those back rather than reshuffling at random, we ended up using mathstutor.me, which is free for a set number of exercises a day and follows the English curriculum. Full disclosure, my DH built it, so obviously take that with a pinch of salt. The Funkey cards and the playing card game upthread do the same job perfectly well if you would rather stay off screens, and honestly the flash cards and the kitchen table method that DominosForDinner described work just as well as anything with a login.
The one thing I would say from experience: consistency beats method by a mile. Five minutes every day, on the same twenty-odd facts, will get you there in a few weeks whatever you use to deliver it.