Hi Peggy and welcome to the fourms! Thank you for taking in a rescue grey!
First of all, these birds operated in what we call "grey time". This is the time it takes for an individual bird to accept changes in their environment- be it a new food, new toys, new people, new cage etc etc. Every bird is different and will accept changes at their own pace. Trying to force the issue will cause a fear response and will damage the relationship with your bird. So it is absolutely critical to observe the birds responses and start learning a bit about their body language.
Body language in grey's is quite subtle at times and sometimes we don't always notice it. A bird can be trying to tell us a lot through their body language and we totally miss it, so the last resort is a bite to get their message across.
Your bird has just had a massive change to their lifestyle. Did you know or interact with your bird at all before bringing her home? If not then absolutely everything in her life has been tipped upside down and she is probably still adjusting to changes. New home, new flock, new environment, new routines... it's a LOT to take in! She will need some time and space to adjust to all these changes. But she will get there and she will accept you as part of her flock. At two years old, she is still a very young bird so I have no doubt that given enough time you will build a wonderful bond with her.
Do you know what her favourite treat is? If not, try offering her lots of different foods and treats until you find one or two she REALLY likes. So for example, if she really likes almonds, do not feed them as part of her daily diet- keep them as rewards. You can then use that favourite treat as a reward for good behaviour - this is positive reinforcement. So if she steps up, she gets a piece of almond (not a whole one - save whole ones for REALLY good work). Do not move away from the cage at this point- just get her stepping up regularly. Always let her go back to her cage or a perch if she wants to at this point. You can then start rewarding her for staying on your hand. Again, use a piece of almond not a whole one. If she's still comfortable and content on your hand for a few more moments, she gets another piece. If she's still doing really well and making no attempt to leave, maybe go ahead and give her a whole piece. Again, always give her the option of getting back to her cage. As she is clipped and maybe unable to fly then always give her the option to retreat back to her cage, as she doesn't have a flight option. Keep talking to her whilst she is on your hand - make it sound like a good thing and sound excited about it. Tell her about all the places she will be able to go with you if she stays on your hand rather than going back to the cage. Make it a fun and positive experience for her.
Once she has mastered this (and it may take some time) then SLOWLY start moving her a little further away from her cage. Reward her for staying calm. If she bites, do not take it personally (even when it hurts!) and just calmly return her to her cage and back off. Keep using pieces of whatever her favourite treat is. Only reward with a whole treat occasionally. This helps to keep the bird motivated to work towards the big treat. Or if she has a couple of favourite treats, find out which she likes better and use that as the special treat.
Keep these training sessions short to begin with. She might not have had much structured training so it might take her a little while to figure out what's going on. Get her to repeat the behaviour successfully a few times then stop. You can slowly extend this if she is willing- but as soon as she shows sign of boredom (or goes for a bite) then back off and let her return to where she is comfortable (a perch or her cage)
Do keep us updated with any progress. We would also love to see photos of her if you are able to.