Now, if you decide you are willing and able to comit to this dog (taking into acount work schedule, finances, and lifestyle). Then step one is to housebreak her... you have to go back to basics just as if she was a puppy. Crate training may or may not help (depending on whether the crate stresses her more or less. If you find the isn't practical, switch to a small dog-proof or blocked off area for confinement. When you are home, use the umbilicord method (leash her to you), so that you can control and watch her, and take her outside when she shows signs of going (firm NO if you catch her going.. then scoop her up and right outside.. LOTS of praise if she goes outside!). Teach her a "potty" command (harder with older dog.. not impossible), so that she associates that word with going to the bathroom and getting lots of praise.. if you can get her to go on command, you will have an easier time of regulating her behavior. The clinginess is partly just a common trait of Maltese, and partly insecurity and separation anxiety. Your best bet is to ignore her when she gets like this (yes, I know how hard it is!), any attention she gets will reinforce the behavior. If at all possible, I strongly suggest an animal behaviorist and/or professional trainer. Make sure the person you choose is experienced in dealing with older dogs, and rescue dog experience would be a plus. You may be able to get a referral from your vet, or your local Maltese rescue group, local Humane Society, etc. As to tail biting, it could very well be stress, but if you haven't had her to the vet you should probably get her a check-up just to make sure (also look for signs of fleas or other areas of biting/scratching, and have the anal glands checked if you don't know how to do for yourself). Once she is feeling comfortable, confident and secure in your home, many of the stress problems should go away. Good luck. I do hope you are able to help this poor little Lady.. whether by keeping her and working on it, or placing her with someone who can.
Aimee