Pretty sure it's no longer on the site:

Anthro fic - Alicorn Twilight is packing massive meat and decides that since Rainbow is always bragging about how sexually experienced she is, she'll ask Rainbow to help her blow off steam on a no-strings basis. What no one knows is that RD is actually not experienced, but still tries to fake it.

Each chapter is an escalation. Something like kissing, to handjob, to blowjob, etc. As things go, RD starts getting attached to Twi and thinks it's turning into real relationship - even practicing with ever larger toys to prepare for final step. But after Twi returns from a trip away from Ponyville RD reveals that she did get attached and Twi is surprised - not realizing her heat-of-the-moment sex-talk had been taken seriously. But, they decide to slow things down and try the relationship thing. Happy end.

Believe the cover art was an ELZombie piece and that it was something like 5-7 chapters.

Think last time I saw it was in neighborhood of 2016, but could be off on that. Do know I've been trying to relocate it for 2-3 years or more by now.

I'm 80% sure that was a story by 'megapone', but they've taken all their stories down. You may be able to find it in an archive (if I'm even right.)

I'm now 95% sure it's 'virgin' by 'megapone', I'll double check after I find an epub reader.

7605004
Thanks! That was enough to find it: Virgin by megapone

7605008
Excellent, glad I could help!

Think you could post the link if you found it?

7605014
PMed.

7605018
Any chance I could also get that link?

7606426
PMed

7606914
Thanks