I’ve heard of the name [name_f]Nadine[/name_f] before, and it sounds perfectly fine to me.
[name_f]Nadine[/name_f] reminds me of this great song by [name_m]Chuck[/name_m] [name_u]Berry[/name_u] 
I like [name_f]Nadine[/name_f].
It’s not flashy or trendy but it doesn’t feel super dated to me because it’s never been very popular.
I actually think it sounds perfect with [name_f]Clarisse[/name_f]. Both names have a suave [name_m]French[/name_m] vibe to me. Like they would be classy, strong women.
For the record, [name_f]Pauline[/name_f] also has the same vibe to me. It’s another unflashy name with a sophisticated feel. I went to school with a [name_f]Paula[/name_f] (she’d be about 30 now) and I always felt it was a statuesque name.
I think [name_f]Nadine[/name_f] is gorgeous and goes fabulously with [name_f]Clarisse[/name_f]. I wouldn’t change it based on family comments - since they’ve also had a hard time with the (very lovely) names your sister chose, it’s probably just them. That’s why I don’t recommend sharing with family before the birth. It gives them time to adjust, but also gives them time to give unnecessary commentary and opinions that aren’t really their business…they’re less likely to do that once the baby is there with all the excitement and ability to put a cute little face to the name.
I would keep it, and any time anyone says anything about it just say “thanks, we really like it too!”
I don’t think there is anything grimace-worthy about [name_f]Nadine[/name_f] and I think it goes quite well with [name_f]Clarisse[/name_f]! I wouldn’t change it just because other people had negative things to say.
My 3 year old is named [name_f]Matilda[/name_f] and I definitely got some reaction at first from people not really liking the name. Not outright rude or anything but a lot of “Oh… that must be a family name?” And people insisting she must have a nickname with a name like [name_f]Matilda[/name_f], they wouldn’t call her that. Now I just have people telling me “She is definitely a [name_f]Matilda[/name_f]. That name fits her perfectly!” And some of these are the same people 
Go with what you love. Like someone else said, your baby will influence what people think of the name. They may change their tune when they see cute little baby/toddler [name_f]Nadine[/name_f] and realize oh [name_f]Nadine[/name_f] is actually really cute!
I think [name_f]Nadine[/name_f] goes perfectly with [name_f]Clarisse[/name_f]!
I have no idea where the Arabic comments are coming from. I know a couple of [name_f]Nadine[/name_f]'s and they’re both my age (mid-30s). Some relatives didn’t really like our naming choices, but they’re our babies, not theirs…
[name_f]Nadine[/name_f] and [name_f]Clarisse[/name_f]!
[name_f]Nadine[/name_f] is a bit dated here. Women in there 30s are na Nadines in NZ! So for me it’s a bit naff. I don’t dislike it, it’s just a bit overused in my generation. I love a pp’s suggestion of [name_f]Sabine[/name_f]. Sounds great with clarisse.
I also think [name_f]Nadine[/name_f] sounds wonderful with [name_f]Clarisse[/name_f]! It also sounds fresh to me, I haven’t met a [name_f]Nadine[/name_f] personally before. Go with what you love!
I love [name_f]Nadine[/name_f]!
And it sounds great with a big sis named [name_f]Clarisse[/name_f] 
I had a friend whose younger sister was [name_f]Nadine[/name_f]… they called her [name_f]DeeDee[/name_f] which I have always thought was super cute! I actually really like the name!
As for family… I make it a point NOT to tell family or anyone for that matter what names I am considering… to many opinions make for a more difficult naming experience! Pick the name YOU like and go with it! They will adjust!
[name_m]Don[/name_m]'t change your mind because of other people’s opinions! If you really love it and don’t use it you will regret it. I think it’s a pretty name
[name_f]Nadine[/name_f] is a great name and 100% [name_m]French[/name_m] to me. Forget about people’s opinions and just follow your heart!
Arab? I always think of [name_f]Nadine[/name_f] as a french variant. I adore this name. Also liking [name_f]Nadia[/name_f]/[name_f]Nadya[/name_f]. I say stick with your choice. What matters is your and your husband’s opinion. It’s a bonus if your family likes the name too, but if you love it and they don’t, don’t let their comments bother you.
Oh, I love [name_f]Nadine[/name_f]! I would be so overjoyed to meet a baby [name_f]Nadine[/name_f]. If you decide to use something different, I’m quite fond of [name_f]Celeste[/name_f] as well.