I think it’s likely she won’t be able to really perfectly fit a standard sized suit. Note that in water/air temps that are just below comfortable it might be ok to live with a slightly ill fitting suit. Once you get in cold temp territory the suit fit should be as perfect as possible.
What I would do: go to a store with a wide variety of wetsuits and a repair shop and fit as many as possible.
If there is nothing that really fits you can try to:
1) use layers, especially if the legs/arms are ok but the torso is a bit to wide consider wearing a shorty wetsuit or are torso warmer below the suit.
2) get someone from the repair shop in the store and see if they think they can maybe customize a suit a bit.
Another option would be to get a full custom suit. No clue how expensive that’s going to be but it probably is not cheap. A quick Google suggest terrapin makes custom suits: https://www.terrapinwetsuits.com/materials/neoprene/