In this particular post I'll talk from my perspective not what we usually see or learn about devi normally 

Meldi maa is worshiped mostly in gujrat and some other regions stories is  when Rakshas name Amruva was fighting with goddess durga for a long time and when he knew  that  he cannot win he basically hid in the corps of  cow/ buffalo and as the form of devi was satvic she can not go in that kind of place and than she rubbed her hand (Mel) and the beautiful 6-7 year old girl was present their what we call as meldi maa and maa durga assigned her task to get that rakshas out of that kankal(corps ) and kill him . Eventually Maa meldi killed that rakshasa and then she was blessed by devi maa like durga , maa chandi , maa sarasvati and at the end it is believed that shiva gave her boon that she will be worshipped in kalyuga like other forms of maa used to be worshipped 

There are three different forms of Maa 

1- Ugta Porni meldi( one who rises before  the surya dev)   

I'll make the whole story of her forms in different post's 

2)  Patali Meldi ( one who has control over patal loka or who lives in patal lok ) 

3) Masani meldi ( one who has absolutely mastery over samshan and dark forces )

From my perspective This three forms represent 3 tatvas 

Ugta porni medli is Satvic and Baal form of  Maa

Patali meldi represents the Rajsik nature of maa 

Masani meldi - Most fierce form of maa and tamsik form.

How to worship her :

Two days are the best Tuesday And Sunday even you can fast on these 2 days 

You can offer red flowers , satvic prashad , fruits and it is better to do diya of oil than ghee .  She is very fast responding , absolutely active in kalyuga 

About Mantra - She is not a puranic devi you can't find her normal mantra  Go with Naam mantra or Navarna mantra with her name ( not without the guru or guide )

I hope this helped people who wanted to know more about her ..

Maa Meldi and her forms