How much would you charge for a Friesian filly that is 0 years old (just born yesterday) with 55K points and lines (not store X store)?

Hmmm, not sure. I don't know if anyone's really sure about a set pricing system for animals on here. You could just make a post about said filly, with all her details and a link to her, and just ask for reasonable bids? I think that's what most people do. 

Pretty much what Sass mentioned is a good idea! :)

I have someone interested but hasn't bid cause they don't know what a good bid is.

I usually sell my Holsteiner babies for 10 million each. But they have 70-90k points. Usually people post in the forums what they have and people bid as Sassafras stated :) 

 If you have someone interested, you can negotiate a price. 

Sometimes I decide to sell a store horse that has points because I'm no longer interested in the breed, or for whatever reason. I sell those horses for around $1-5 mill each depending on the 1) popularity of the breed 2) points-to-age ratio 3) how quickly I want the breed to sell

Since Friesian is a popular breed, you already have an interested buyer, and it's a pointed, lined horse, I'd say $5-$10 mill is what you might want to negotiate. I guess you kind of just have to decide how much you think is fair for the filly. 

As a ball park figure I will pay around 5 mill for a 70k foal. I paid 15 mill for 145k pups. So for me a 55k foal 1-2.5 mill

I'd probably be willing to pay around 3-5mil, depending on the quality of the lines maybe a bit more.