Nice boss character design. =P Anyway, please note that I'm still not very 'proficient' against her, so anyone is free to add in their own tips and strategies. =)

1. In dragon form, she will continue to fly all over the place charging at you for a few times, all of which you’ll have to side roll away from. In the harder modes, she may also dispatch seeds while flying around; jump to avoid.
    
2. It's hard to attack while she's in dragon form, so instead of attacking, it could be useful to use this time to charge a Charged Shot. (Charged Shot LV3 would be awesome for damage) Release it when Echidna changes her form and reveals herself.
    
   
3. When she floats around with her real body revealed, you are likely to resort to Nero’s aerial attacks for attacks. Mixing Aerial Combo with Roulette Spin (/\ /\ pause /\) should do the job well enough for both damage and style.
    
   Typical attacks she’ll do at this time is a 360-degree tail sweep, or her ‘hair’ swing attack, both of which you can jump away from.
    
   
4. If you’ve damaged her enough, she’ll get dizzy for a few seconds during which she will not attack. Slash her a few more times and then press O by her face (like the rest of the bosses) for a DB attack. Note that if you have DT released, the DB attack will damage more. Also, mash [] during the DB sequence for additional damage.
    
   
5. Another form Echidna has is this seed-laying form where she’ll spawn a single Chimera Seed. At this time her belly is open to attacks, but since it’s in mid-air once again you’ll need aerial attacks to hit it. Slash it as many times as you can and before she changes her form, press O by that belly for another Buster. (DT for maximum damage)
    
   Just so nothing screws up your camera angle/lock-on, I suggest that you kill the Chimera Seed with Buster for an instant kill before you Buster Echidna.
    
   
6. Another form is where Echidna sits on the ground revealing herself with her tail under the ground. You can attack her at this time but be careful of her tails sprouting out of the ground; they will knock you away from her. She will also do the hair swing from time to time.
    
7. After taking her life down to about 3 bars (or 5-ish for DMD), Echidna will start flying all over the place like in her dragon form, only, she remains revealed.
    
   As usual, she will charge toward you, but instead of side rolling/Table Hopping you can now press O for another Buster when she's close enough. It'll require just a bit of timing. (Thanks to Marvin for the tip)

Video demo on DMD | Mirror link on Youtube
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