Even if Meghan wanted to maintain a friendship with him, she couldn't! Princes Harry and William hate Piers because he was the editor of tabloid the Daily Mirror in the 1990s. That very tabloid was partially responsible for the death of their beloved mother Princess Diana. They created a high demand for her pics, and that is why the money-hungry paparazzi were chasing after her to begin with. Dude was also implicated in the phone hacking scandal (members of the Royal family had their phone hacked), and the Prince's tragically lost their mum as a result of that very same invasion of privacy. Obviously, you can't associate with certain people once your in the Royal circle and I imagine Piers Morgan is near the top of that list. Meghan's standing with the Royal family, and her relationship with Harry would definitely have been jeopardized.
Piers also gave her toxic family a platform to publicly harass/embarrass her and some of his remarks have had racist undertones to them. There's been some kind of smear campaign in the media towards Meghan this week, everything from her alleged feud with Kate and being a snobby cow towards Royal staff. I hope she's not reading all that stuff as it's quite hurtful and no one needs to be reading that about themselves while carrying a child.