My 5 month old long haired chihuahua is amazing indoors but when She goes for walks it takes a while To make her walk and is petrified of any other dog no matter what size.

She will sit by another dog but will not let any other dog come closer and runs away and starts to cry!

HELP!

I would take things very slowly with her and don't make her do anything. When I had a toy breed I got them used to a collar and lead in the house first of all. Then would carry them outside, just a few yards and then let them walk back in, to a tasty reward.
Small dogs are very often happier to walk home on the lead than out to start with. Take her out a couple of times a day like this, and gradualy progress, if she is worried go back a stage. Usually you will be down the road and coming back quite quickly.
Once she is enjoying her little trips out, you can then try encouraging her to walk out on the lead, use plenty of treats of high value, chicken or some boiled ham worked best with mine.
But take things at her pace, lots of encouragement and a happpy voice.
With regard to other dogs I would not force her to meet other dogs, let her keep her distance and just watch for the time being, and then when she is more confident, gradually introduce her to some calm dogs, preferably small ones to start with, and see how it goes. If she just wants to sit and watch, but keep her distance that is fine, just give her plenty of time, and make sure she is not frightened by other dogs. Some dogs need a bit of time and like to keep their distance, but are taking everything in and learning by watching other dogs playing and interacting together.
It sounds as if she has missed out a little on her socialisation as a young puppy, so she now needs to make up for this, it will take time and a lot of patience. I would also ask about socialisation classes at a dog training class, if you explain to the trainer about her, they may let her socialise with the baby puppy class as she is a small breed. A good trainer will have come accross a puppy like your before, if they try to force her to do anything or tell you to pull her, or force her in any way, walk away and find another trainer. The more you do at this stage with your puppy will be invaluable later.

The world is a scary place for someone Chi sized, if you doubt that, get down and LIE on your front on the pavement as cars whizz past and then see how intimidating the world looks.

So - tiny steps, never ever push her until shes backing off and worried - instead, step out of the front door, reward heavily for one or two paces away from the door, then turn around and go back in. If she cant manage getting out of the door yet then lead on, reward, door open, reward, close door take the lead off..

You can repeat these short sessions several times a day, the end result for each one though HAS to be 'ooh I wish we could have done that a bit longer', ie you leave her wanting more, rather than being fearful and hating every second of it.

I would combine this with carrying her around in places shes ok with, again lots of reward EVEN if you think shes ok with it - we forget to do this classical conditioning when a dog seems ok with something and it is really silly, as the saying goes, an ounce of prevention is better than a ton of cure!

For treats, I would go with Primula cheese spread - much easier for the dog to eat (stressed dogs dont want to so rewards that involve chewing are not as good as licky rewards) and much easier for you to give a high value reward (the stuff STINKS particularly the ham flavour) without actually giving a huge amount of food.

For other dogs - as Dorcas says - don't force her to meet them. In fact make a habit of avoiding other dogs - she does not need to meet everyone, nor be friends with every single one (those things are really human desires, not doggy ones!), she needs to be comfortable and relaxed in the presence of other dogs, and the first stage to that is trusting that YOU will handle the presence of other dogs so she has no need to do so. Stay calm about it but turn around, step out of line of sight, cross sthe road, run away (make that a game!), whatever it takes - you may need to be assertive with other owners, you may need to pick her up (if thats going to be frequent then TEACH her to ask to be picked up so that she thinks being picked up is a nice game rather than a panicky fear related thing)

Once it has become a habit for you to avoid other dogs, start rewarding her for seeing them at a distance where shes ok (probably  a pretty big distance) and start looking around for sensible calm dogs with nice owners who will, eventually, allow you to parallel walk with them and organise little meet and greets.

>It sounds as if she has missed out a little on her socialisation as a young puppy

It certainly does!  Big time!  It is so sad that this breed is being bred for the pet market with no attempt to treat them as dogs.  Mine are allowed to play in the compost heap with the Collies.   And they are using Collie tails as raggers by 5 weeks!

Fear at this age is down to the breeder, who has the opportunity to ensure pups don't turn out to be nervous.  I see it so often.  I saw someone with a snappy growling Chi at the vets, and she boasted that the dog needed to be muzzled to be examined by the vet.  While my tiny tot was busy making friends with a Labrador. 

To the OP
dorcas has given sound advice.  At this age you really do need to move very slowly.  A lot slower than I move with young pups!  You will need patience, and Good Luck.  :-)

Thanks guys. The walking part isn't as bad as it sounds. She will walk for 5 mins pooh and pee and then he thinks it's time to go home and will want To go home. But when she gets to the park she loves it'