Wobbly female bullfinch

Hi, we have a visiting female bullfinch who is very wobbly, she is always fluttering her wings to stay upright and is unable to get in to our feeders.  Is she just made wrong or do you think she is poorly?  She's been around quite a while.   We have had fat finch disease in the garden previously (now very rigorous with our cleaning etc) but never seen a bird acting like this.  Any ideas? Thanks.