Or should I respond at all?

Essentially, LTR of one year ends things with me a few weeks ago because she's "unhappy". We had split up once before but restarted, which was actually one of the major factors in me getting my life back into gear last year, getting a job and getting more serious about lifting and so on. But anyway, this most recent time we stay sort of talking which was unsatisfying to me, I had a bit of a oneitis for this girl so was struggling a bit to let it go completely. All this time however I am talking to/banging other girls to help myself get over it and back on track, I sleep with three new girls in the space of about a month.

Through social media (go figure) she finds out that I've started talking with someone who I genuinely had no idea is her exes ex. She then uses this as an excuse to get really mad, jealous and say some really nasty shit to me and we have a big fallout. Remember all of this is after she ended it. I get a bit mad, then laugh it off and continue as normal as that was a big step towards me moving on with my life. I lost any ability I had to take her seriously at all at that point because it was such typical jealous bitch shit.

Now a couple of nights ago she sends me a big long message apologizing for that, and for how she behaved during the relationship, saying she hopes I'm okay and all the rest of it. I have ignored it for now and presumably I should continue to do so. Seeing it did bring up some conflicted feelings so I'm probably not entirely over it yet

Is this just an attempt at getting closure and satisfying her own desire to not feel bad? What's the appropriate response, or is the best response no response at all? This has never actually happened to me before so am unsure how to proceed.