RCS messages work on Iphones now!! (maybe?)

It's not a carrier issue, Apple has made it very clear it will not include support for RCS in its iMessage platform. For now, all we can rely upon are the dated SMS and MMS protocols for any interactions between Android and Apple users for texting.

Apple does support SMS (text) and MMS (text including attachments) in it's iMessage app so any text messaging exchanges between Android and Apple users involve the transfer SMS/MMS. Currently, all Apple users have iMessage support, and all Android users have SMS/MMS support with Google making a hard push to have RCS become the default text messaging protocol instead. If that happens it will be a matter of iMessage for one side and RCS for the other.
Both SMS and MMS are very dated protocols and have trouble with today's technology. But they are the only common link as far as text messaging. Apple's iMessage is a very expansive, comprehensive message service where all traffic flows through Apple servers. This allows Apple users less restrictions as far as things like file size limitations that MMS has. So all iMessage to iMessage exchanges go through Apple servers. But an Apple to Android exchange involves transfer between carriers and operating system platforms with MMS involved. It's the same with WhatsApp -- WhatsApp to WhatsApp exchanges go through WhatsApp servers involving the also comprehensive WhatsApp protocol. But the same with a WhatsApp to Android user has to involve a SMS or MMS transfer.
With competing proprietary protocols that different corporations rely upon and they don't involve compatibility so SMS and MMS are remain as the weak link between services. Apple refuses to allow other platforms to use its iMessage protocol so legally no one else can include support for it in their own development, and even though Google's RCS has no Android-only restriction, this creates a text messaging limitation where the only universal solution is still SMS and MMS.

Again, MMS is a very dated protocol. It has very antiquated limitations and things like large file attachments are going to be problem. A lot of carriers will do on-the-fly scaling down of high res photos and videos to compensate but the end result is the receiver will end up with scaled down,low quality media files. Or there it simply fails. That's why Apple and WhatsApp use their own proprietary protocols by default, to avoid these kinds of limitations. File size limitations are rarely a problem when it involves iMessage to iMessage exchanges. It's also not a problem with RCS to RCS exchanges. But since Apple is refusing to include RCS support nor can other platforms include iMessage support (legally) in their messaging services, that's the problem.

If you want to send a photo or video to an iMessage user, you can scale it down yourself to meet whatever arbitrary file size limitation your chose carrier applies (they all will have those specs posted somewhere in their web site).
Or if you're using an online file storage service (Dropbox, Google Photos, OneDrive, SpiderOak, etc.) you can obtain the sharable link for those files and just send the link to your recipients.
Another option is to use a file sharing service like Firefox Send:
https://send.firefox.com/
Despite its naming it's browser agnostic so you're not limited to just using Firefox. Upload the file you want to share and it provides you with a sharable link. It's free to use with limitations (1GB per file), or if you have a free Firefox account the limit goes up to 2.5GB with a lot more options for access and time availability.

OK, my bad. It's a matter of being able to send larger sized files to your wife but doing the same to other recipients it fails.

This is likely to be a carrier issue then. Exchanges of MMS between carriers will involve those MMS file size limitations and they often won't work over WiFi, they involve transfers between the cellular networks. (SMS is very low bandwidth, you just need the base cellular connection, MMS involves mobile data). Text messaging is a convoluted mix of standards and incompatibilities.
Forgot mention before there's always email too for exchanging file attachments. A lot of email services allow up 20-25MB per file, or more.

Does it send the video, or does it send a hyperlink from which she can download the video?