My dog is fairly large (border collie), this won't be what you want to hear, but I started off a massive dog lover and pretty confident around dogs, I grew up in a 'rough' area where it was all pit bulls and status dogs, I had family members who fostered GSDs.
I am however now seriously wary of other dogs, due to their owners.
I have had many, many scary incidents with other dogs and my dog.
Dogs running over to attack her when she hasn't even seen them, owners demanding to say hello then their leashed dogs going for her, overly boisterous dogs jumping on her and hurting and scaring her.
I have had quite a few dogs go for me when I have been on my own too, DH has been bitten twice by the same leashed dog when walking alone.
I try to avoid other dogs, both when I am walking my dog and when I am out and about without a dog.
If I see another dog with my dog we walk at heel past, no stopping to say hello.
If both are off lead I watch carefully, if my dog wants to approach and the other dog seems to have good body language I allow a meeting.
Usually, off lead I recall my dog if the other dog looks like it's going to approach her.
Unfortunately, you can't pick up a 15kg collie and stuff her in a handbag.
If she was a chihuahua and I saw a larger dog off leash I totally would.
I wouldn't let it socialise with other dogs apart from my own or other chihuahuas/similarly sized dogs that I had met prior.