Training for recently adopted Yorkie

[Whitchick]

Morning all, I was wanting some advice. Last week I took on a 6 year old female Yorkie, her owners had her in a flat and she was left for endless hours on her own, so we've taken her on. Overall she is very good, she has settled quickly, her old owners complained about her wetting constantly and the marks on their carpet backed up their story, apart from her first night with us when she had a small accident, she has been clean, but has access to our garden and we've got her straight into a routine of regular walks and mealtimes and so far so good. She is generally very placid and well behaved, walks well on and off lead. However, she has got a terrible habit of running up to other dogs, and is very excitable around them, a little dog this morning snapped at her. If she is on her lead and sees another dog, she makes a terrible fuss, yapping and straining at the lead to get over to them. I dont think its aggression but equally I dont want her getting into a fight with another dog. Can anyone give me advice on how to deal with this ? She loves being off lead but I am frightened she or another dog might come to blows. The other thing is, she chases cats, I have four. She wont chase one of mine, who clearly isnt scared of her, allows this cat to walk freely through the house, sits on the bed with her etc, but the other 3 younger cats she cases constantly, despite me telling her no and doing what I can to stop her bothering them, I've always kept dogs and cats together but I worry at 6 years old she cant be retrained. I also wondered on the odd occasion when she is going to be on her own, whether I should crate her?? - so looking for some advice from experienced owners