No offense to your friend, but if she is saying she is both an ENFP and an INFP, then she is probably not very well versed in MBTI.
Because you can't be both? OK
The mind is incredibly adaptive. It's very possible to be a switch type. Hell, I'm one (INFJ / ENFJ). All it takes is very borderline Introvert and Extrovert scores, and the ability to shift back and forth depending on social demands. It is not uncommon for people to be able to do this if they have well developed dominant and secondary functions.
NFPs generally don't like labels due to Ne mixing with Fi, and the idea of not fitting neatly into a box tends to appeal to them, which is probably why your friend never bothered to pin down which of the two types she was borderline on was her base type. She was close to both. Both descriptions seemed to equally apply. Next.
It took me over a year to decide on which of the two was my base type. That's a lot of time and effort to solve an enigma. I can see why she just accepted both and moved on.
Anyway...
I've dated a handful of INFPs (as in 4 of them were included in the 7 very significant relationships of my life), and the relationships never worked, no matter the colossal attraction we had for each other. It's just crazy how not well suited we ended up being, because in all cases there was insane chemistry. These relationships had an intense amount of attraction and love, and they really should have worked but they never did, and for very similar reasons every time. It was like we spoke the same language but our words meant different things.
Last year, I dated an ENFP. I've never been in such a roller coaster coaster relationship. It was like her emotions were entirely based on current circumstances. Some days she was crazy about me. Other days she was interested in some other guy (never the same one, mind you). Some days, she'd switch who she wanted to be with while we were on a date. And she'd jump all over the place emotionally, and expect me to not only accept this behavior, but support it. When it upset me, she'd get mad at me for being upset.
In other words...
I find NFPs to be very attractive, but I've learned the hard way that all that glimmers is not gold, and NFPs are my kryptonite.